During the scene in the mall when the girl is in the dressing room, she keeps putting on more layers of clothing. But as they are shooting different shots she will have a hot pink shirt on, then it is back on the hanger, and then back on again. It switches back and forth many times.
"Evolution" was originally written as a serious sci-fi thriller by writer Don Jakoby. When Ivan Reitman signed on to direct, he felt the concept would make for a good ensemble comedy, similar to his film "Ghostbusters." Jakoby actually liked the idea of reworking the film into a comedy so much, he stayed with the project and assisted in re-writes.