Insectosaurus is a major character in the Monsters vs. Aliens franchise. She is a parody of Godzilla and Mothra. She was once a little caterpillar who was turned into a gigantic insectoid monster by nuclear radiation and attacked Tokyo.
Insectosaurus originally was nothing more than a simple grub with no unique characteristics, but after her mutation she donned an almost mammalian-like appearance similar to that of an orange hamster with a massive overbite, four pincer-like arms, antennas, two stubby feet, and a short reptilian-like tail. Insectosaurus is a massive creature in size even dwarfing the giant Ginormica. She is seen in the movie using her powerful pincers to pull the bridge back in place in the Golden Gate fight scene. Not only can she do that, she can also shoot sticky web substances from her nostrils that were used only on the Alien Robots eye to stop it from reacting for a short time so the other Monsters could get her and Ginormica (Susan Murphy) to battle Monster on the Golden Gate Bridge. Although of her big physique, she is actually a baby, but that is not approved other than she cannot talk. When she walks, she does that in a dinosaur way and is very slow to walk. Sometimes she doesn't know what to do so she is mesmerized and navigated by a helicopter carrying a light in front of Insecto causing her to stare at it and follow where it goes, also it helps keeps her stable and be amazed at the sight. When that happens, the pupils of her eyes grow almost as big as the size of her eye making her look like a big scary looking monster, but really she is the cutest thing in the film! She cannot hear what the other monsters, aliens and humans are saying (Apart from the Missing Link) so that makes her an (almost) useless, powerful, fun, cuddly Monster.
After her metamorphosis near the end of the film, Insectosaurus' appearance is changed to that of a more butterfly-like creature (similar to Mothra of Godzilla fame) while still possessing her hamster-like face, furry body, massive overbite and reptilian-like tail. She's been renamed to Butterflyosaurus.
- For some inexplicable reason, Insecto never appeared in the TV series, nor was she even mentioned.