Preliminary drafts of Evolution by Don Jakoby elaborated the premise of the story with a much more serious tone compared to the final film. Upon being hired for the project, director Ivan Reitman requested screenwriters David Diamond and David Weissman to shift the script into a comedic adventure sci-fi story, in the same vein as Reitman’s Ghostbusters films. With only a full year before the film’s intended release and a whole alien ecology to bring to life for it, Reitman immediately began seeking the right effects craftsmen for the project. “This wasn’t about one dinosaur,” Reitman said, “or even a bunch of dinosaurs. It was about creating a whole new world.”

Visual effects producer Nancy St. John and concept artist Yuri Bartoli joined the project early on. “Working with Ivan was a lot of fun,” Bartoli said. “He was open to new ideas, so you could bring anything to the table. But he knew exactly what he liked and what he didn’t like. That helped me, because I could channel my efforts in a direction that was in sync with what he was looking for.”

St. John immediately knew that Tippett Studio would be ideal for the type of needed visual effects work. “This is a Phil Tippett show,” she told Reitman in early production meetings. Her impression would be proved correct. Tippett recalled: “I have a real strongway of saying, ‘I think this is the way this stuff ought to be done, and if you don’t want to do it that way, fine; but then I don’t want to do it.’ But I was very comfortable with Ivan from the start, and I think he was with me.” Tippett Studio art director Peter Konig began focusing on creature designs, from the single-celled organisms seen at the beginning of the film to the massive amoeba monster of the finale. Tippett related: “we had a couple of production meetings with biologist Dr. Mark Shelley, laying down ground rules for the whole thing. The aliens that come to Earth on a piggyback ride on this meteor could have been really weird and wacky; but gradually, we narrowed our ideas down to those based on the notions of ecologist/philosopher Phillip Gould.”

According to Gould, evolution on Earth would never take the same path twice — its results are not duplicable. Different forces and processes would result in wildly different outcomes — and that was the fundamental premise of the alien designs. The idea on paper was that the aliens share the aesthetic of Earthly life because they took upon Earth DNA upon landing. “The alien crashes,” Tippett explained, “and whatever it is, it’s life. It takes Earth’s DNA, crunches it up, and starts up a parallel track, an accelerated path that moves through our terrestrial evolutionary development: single cells to multi-cells to flatworms to crustaceans, insects, amphibians, reptiles, and on and on. The premise necessitated that we create that entire evolutionary arc.”

Reitman himself agreed that the look of the aliens should have a connection to Earthly animals. He related: “they were aliens, but there had to be some sense of reality about them — exaggerated forms, perhaps, but something with which we could still identify.” Reitman reviewed concept drawings and maquettes weekly, and however fantastic the creatures conceived in the design phase were, the team soon had to face the logistics of actually bringing them to the screen.

Tippett explained: “it is always a numbers thing. We know we can do this many of this kind of shot for this many dollars in this amount of time; and the studio says, ‘I don’t want to pay that,’ and the director says, ‘I want more shots.'” Given Reitman served as both director and producer, budgetary discussions were somewhat eased. Tippett continues: “Ivan had to wear two hats, and you could actually see him switching. As the director, he’d say, ‘I want all this stuff’ — and our eyes would roll back in our heads, and we’d say, ‘oh, man, you’re never going to be able to do all that.’ Then he’d say, as producer, ‘okay, what can I do?’ And then we could start talking reality. There was a lot of negotiation; but it wasn’t contentious, and it worked.”

The final roster amounted to around 18 creatures — some of which were alternate versions of the same basic template. Those translated approximately to 200 animation shots, a number that rivaled the Tippett Studio shot count in Starship Troopers — with the important difference of a much lesser time in which the crew could produce them. When the release date was moved further up of six weeks, Tippett and St. John decided that the workload of visual and physical effects would have to be shared between several companies. Tippett Studio retained the majority of the effects shots; Pacific Data Images produced the opening meteor sequences and some of the primitive lifeforms seen early in the film; Sony Pictures Imageworks was assigned certain insert digital shots; KNB Efx produced a number of physical effects, including dummies of the alien dragons; Amalgamated Dynamics was instead assigned the creation of the alien primates.

To ensure consistency, most creature designs — except the primates — were produced at Tippett Studio, with concept drawings, maquettes and reference materials passed over to PDI and KNB for their tasks. Reitman also reviewed the design process weekly and was the final decision-maker on every detail of the alien creatures, their ecology and their habitat.

By the time all companies had been assigned their tasks, there were only weeks left to deliver certain shots — and in some cases design work had yet to be completed. St. John recalled: “it took a lot to get the design process up and working in the beginning. We wanted to have all 18 creatures designed and finaled before we started shooting. We did fairly well — we were only short by about four, and one of those was the amoeba-like organism.” This schedule resulted in a compressed design process. Creature iterations evolved even concurrently to the creation of animatics for major sequences; and as principal photography began, some shots were still in the conceptual phase, whereas others were being finished.

Every creature, once finalized, was sculpted into a maquette (principally by Peter Konig and Damon Bard) and cyberscanned; some maquettes — such as the Tiphibian — had to be broken down and scanned in parts. The resulting digital model was then refined manually. Colour scheme maps were hand-painted, whereas displacement maps provided texturing and detailing.

The evolutionary cycle begins with primitive single-celled and multi-celled organisms created by PDI based on Tippett and Bartoli concepts. Sony Pictures Imageworks was instead responsible for the flatworms that followed, always based on Tippett Studio concepts. “We added a viscous layer on top,” said SPI visual effects supervisor Jim Berney, “a coating that was kind of cloudy and revealed glimpses of various organs. It added a lot more depth and texture. Depending on the angle, you could see through the outer tissue, and into the veins, then past the veins and farther in.”

A combination of key-frame animation and a flocking tool — recently developed by the company — was used for the flatworms. Individual worms were animated manually, then replicated into thousands of them with the flocking system, which assigned a random, organic motion to the numerous layers of digital worms. Imageworks also produced images of the flatworms reproducing, as Berney explained: “we actually got the innards of the flatworms to pull themselves apart and duplicate. They slowly divide as the membrane rips apart. It was a pretty tricky effect, particularly as we had to do it in a month.” Various practical dead flatworms were devised by KNB.

Gray discovers a trail of flatworms, which leads him to a water tank with an aquatic creature within. This ‘leech’ alien was designed by Tippett Studio and animated by PDI. The next spawn of the evolutionary cycle is instead an amphibious monster that emerges from the a golf course lake, snatching an unfortunate country club member. This creature, dubbed the ‘tiphibian’ by the crew, was designed by Peter Konig. The design combines reptilian and mammalian characteristics: its skull, fundamentally based on that of a horse, is endowed with protruding teeth. Exposed gums and goat-like eyes complete the look of the head, whereas a hairy hump lines its back. Its colour scheme was based on predatory cats. While the living tiphibian was portrayed with a digital model, the dead Tiphibian brought by Gray to the professors was a foam latex dummy provided by KNB.

As the invasion spreads, a strange monster — dubbed the ‘cutie pie dog’ by the crew — is discovered in a household. The mild-looking creature suddenly opens its mouth, revealing a second turkey-like head on the end of a muscular tongue. Reference for the facial movements of the cutie pie dog was taken from the film Milo and Otis. “It had some awesome stuff with the pug that gave us all the looks we needed for the cutie pie dog,” said animation supervisor Eric Reynolds, “the surprised look, the angry look, the sad look. At first we thought, ‘we can’t pull this off. All we have is this smashed face with big eyes.’ But it actually worked.” The crew devised a library of five main expressions; the animators could segue from one to the other using slider controls. Other animations included the body jiggling with the creature’s motion and the ‘wheezing’ action that occurs with its death. As with the tiphibian, a dead cutie pie dog dummy was created by KNB.

Meanwhile, the original alien habitat has developed further into a full primitive environment, inspired by depictions of Carboniferous forests. It was designed by Michael Riva, who worked in close collaboration with Tippett and the director. Riva then supervised the creation of the cavern environment, a full 360-degree set. The same basic structure was dressed and redressed for three cavern sequences, to portray the development of the alien flora and fauna. St. John explained: “the first time we see the cave it’s very small; then it goes to a kind of Alice in Wonderland sequence, with a cheerful outer-world appearance. The third cavern looks mean and ugly, with everything dark and gloomy, black and sinister.”

The set was digitally scanned to devise a double for digital creatures to move in. Visual effects co-supervisor Frank Petzold noted: “we were given enough digital information to create a highly detailed model within which the digitized creatures could move in an entirely convincing manner.” Lively fauna flew, crawled and slithered in the environment: Tippett Studio devised several digital arthropod-like aliens, including: the centipede-like ‘swarm crabs’; coconut crab-like creatures; a large predator dubbed ‘butthead’ for the shape of the back of its head; and a bizarre millipede-like creature with a head on each end of its body, which is quickly eaten by a carnivorous plant.

One of the creatures — a mosquito-like insectoid, dubbed the dragonfly — penetrates Harry’s body. The most challenging aspect of the character animation was the quick buzzing wings. Brennan Doyle, part of the crew, related: “the wings had to move fast and there had to be motion blur, but you still had to detect the shape of the wing within that blur.” The mosquito shape moving around within Harry’s body was a PDI effect.

New, more advanced aliens are discovered afterwards: a valley houses a graveyard of dead or dying dragon-like creatures, a combination of digital animation and practical models. Design of these monsters — including the ‘wal-mart bird’ that wreaks havoc in a mall — began as more bird-like, as opposed to the final incarnation whose appearance is more reminescent of lizards and pterodactyls.

Konig recalled: “it took many, many versions to come up with something that Ivan would go with. The sketch of the wal-mart bird that he finally picked after so many passes was one that we were actually about to throw in the garbage. We learned to always bring all the stuff we had — even the stuff we didn’t particularly like.” The final design was delivered late into production, when certain scenes involving the creatures had already been shot.

In fact, a scheduling conflict created the particular situation where the practical monsters had to be completed before their digital counterparts were even modelled. The inevitable consequence was the rise of design issues of size and colour schemes.

Nicotero recalled: “the size kept changing. One day they were 18 feet; the next day they were 22 feet. Also, the Tippett guys gave us the colour scheme Ivan had signed off on, and told us we had to match that; but we were building eight of these ‘birds’, and we didn’t know whether there should be some variety or if they should all look exactly like the approved colour scheme. We had to be in agreement about such design issues, because Tippett Studio was going to be replicating hundreds of these things in CGI.” Once colour and size were nailed down, KNB crafted eight full-size dead ‘bird’ puppets, with flexible armatures inside so that they could be put in different death poses.

Towards the end of the sequence, a ‘momma bird’ in its death throes — a digital creature — regurgitates an egg sac from which its offspring emerges. Reynolds recalled: “each morning we’d sit up here, and Phil would say, ‘what can we do?’ One thought was that the momma bird could just spit out a wet bird, or spit out a pod that had a hard shell that would crack. We said to Phil: ‘either of those two would be okay. Just, whatever you do, please don’t make it a sac.’ And of course, that’s what they came back with — a sac.”

The birth sac was especially challenging to visualize and produce as a digital element. Its most problematic characteristic was the amniotic fluid-like substance encased within, because — Reynolds explained– “modelling anything that’s soft and squishy and translucent is tough.” Ultimately, Tippett Studio used multiple approaches: views of the fluid inside the sac were performed by tweaking and slowing down stock water elements in the Studio’s library; more elaborate shots of the goo as the newborn monster emerges employed a dynamic particle system. “The animator attached points by hand,” Reynolds continues, “and then the software calculated what would happen to the goo when, for instance, the creature’s wing lifted up and stretched the goo out.”

The ‘bird’ flies away and enters a mall — originally supposed to be a wal-mart mall, hence the production nickname of the creature. The monster was an almost entirely digital creation, with full-size practical insert talons supplied by KNB that carry off the woman in close-up shots. “All the close-up flying stuff was done with this pair of arms,” Nicotero said. “Burt Dalton built a steel armature that they could fish cables through. The cables would come out the underside of the bird’s claws and attach to a stunt harness the actress was wearing. Alex Diaz sculpted the talons, and David Wogh built the mechanisms inside.”

The cavern seen after the mall scene has taken on a more sinister appearance — and the viewer is introduced to the next stage in the alien evolution: primates. Unlike most of the creatures crafted for the film, the apes were entirely developed at ADI, from design to practical construction. ADI co-founder Alec Gillis said: “one thing that’s a hallmark for the work that comes out of our studio is that no matter how outrageous the story, there have to be a certain number of elements that are believable and realistic. So even though we were doing these outer-space creatures, we still wanted to put in enough trademark fatures for audiences to say, ‘I recognize this. There’s something oddly realistic about this.’ We turned to primates as our key reference, because one of our directives was that this had to be a guy in a suit.”

Proportions of the creatures’ form were altered to make the underlying human performer less obvious. Gillis continues: “we tried to make the legs look a little longer, make the arms look longer, put the head up high and make the neck long. The object was to come up with something that was strangely human, but still suggested that it came from outer space.”

Reitman supervised the design process. ADI co-founder Tom Woodruff related: “we started with sketches, and met with Ivan to narrow those designs down to the ones he liked. Then we started building maquettes. Once we had maquettes done, Ivan chose a body and a head that he liked; and, in Photoshop, we combined them and completed the image of the creature.” Ryan Peterson designed the face, while Jim Kagel did body designs; Steve Koch spliced the separate elements together digitally.

One of Reitman’s requests was that the primates had to sport a blue colour. Gillis related: “at first, I thought, ‘eeew, blue apes!’ But once we started doing the design, we realized that it really did work, especially in pale blue. Pale blue skin with pink eyelids and pink lips really had a striking look to it.” Reitman also requested a large, gaping mouth with prominent teeth. When the suits arrived in the cave set, the director noticed that the teeth did not look like the approved version. Gillis remarked: “Ivan has a very good eye. He asked us, ‘did you change the teeth? The teeth don’t look right.’ And we said, ‘no, we don’t think the teeth have changed’ — but the teeth had changed. We asked Dave Penikas, our mechanical designer, about it, and he said, ‘yeah, I had to cut some of the teeth back so I could make the jaws close.’ So we had to go back and fix that.”

Of the seven suits crafted by ADI, one was a hero suit endowed with a fully-animatronic head with silicone skin, performed by Woodruff himself. The 15-pound head was operated by four puppeteers. The suits also featured full arm extensions, and the performer’s head was housed in the creature’s neck (with eyeholes just below the chin). Glowing eyes were experimented with, as explained by Gillis: “we had made some attempts in earlier shows with Scotchlite eyes and internally lit eyes, but they always had kind of a phony look. We decided to use metallic paints on this one, so they would reflect more like the eyes of a real animal. We gave them a very broad, flat base, so there would be a maximum area or reflectivity.”

Three ‘secondary’ suits with more limited functions were devised. Instead of silicone, they had a lighter-weight foam latex skin. The remaining three were ‘third-tier’ suits and were essentially background suits, without animatronics. The third-tier suits were originally supposed to be seen in silhouettes or long shots, but Reitman was impressed with them to the point of using them in certain foreground shots.

Kane and team discover that heat accelerates the growth rate of the aliens exponentially — something shown when a match hits a petri dish, unleashing the growth of a primitive organism (an entirely digital creation inspired by fungal growth). This is also proved true when napalm bombing causes the entire alien habitat to be assimilated by a growing amoeba-like organism that reaches vast proportions.

The amoeba creature’s design was being revised even as shooting was wrapping up. Tippett related: “as the schedule began to snowball, the more difficult things like the giant amoeba got pushed back — especially since nobody knew what it was. We knew what a crustacean would look like, or an amphibian or a pterodactyl bird. We could get a fix on that; but this was some amazing thing no one had ever seen before. So we took many, many paths on it. At one point, I just got out my hot-glue gun and made these tiny little five-legged blobs. We had another take where the thing was much more see-through, where you save organelles and big cells and weird stuff in it. Eventually, Ivan opted for a much more material look, one that had a hard surface on it, kind of like a big placental slug.”

Tippett continues: “we had to imagine it dynamically — actually see it moving; and the more we did that, the more we realized that an amoeba is an abstraction. It’s not a creature like Godzilla or King Kong, it’s much more like a giant tidal wave or a twister. It’s a force of nature.” A tentacled maquette designed by Hayes and sculpted by Bard and Konig was scanned to provide the basic digital model.

The main challenge of the amoeba creature was conveying scale. Visual effects supervisor Brennan Doyle commented: “we found that the best way to convey that scale — in addition to having characters and vehicles in those shots — was to have the creature break frame. It would come down from the top of frame, for example, and the camera would move up as if trying to get the entire thing in frame. We also added camera shake when the creature brought down a tentacle and impacted the landscape. A creature of that size would make the entire area rumble as it moved across it.”

Although the creature was mainly a digital effect, Tippett suggested to build a practical section that could be seen in close-up, interacting directly with the actors for the scene where dr. Block inserts a fire hose into a remarkably sphincter-like opening and injects the amoeba with selenium. KNB devised the full-size practical section based on a Tippett rendering. The section was cable-operated and required 12 puppeteers to maneuver. “The whole thing would flex and pulse like a living thing,” Nicotero said.

Doyle concluded on the experience of working on the film: “I think the reason a lot of us got into this line of work was that we operate well under pressure. We’re in our best form when we’re juggling 18 creatures!”

For more pictures of the ever-evolving aliens, visit the Monster Gallery.