The Pollywollyoptasaurus was an extinct dinosaur that Timmy wished back to life to use as his show-and-tell project in the episode, "Transparents!".
This small purple dinosaur is pretty docile, and is tiny enough to be held in one's hand, although it has a tendency of spitting up a harmless green goo into nearby people's faces. Like all dinosaurs, it has been extinct for millions of years, so one can only acquire one by having a fairy godparent and wishing for it.It is the oldest thing to appear on Fairly Odd Parents.
This creature is smaller than a cat, and is described by Timmy Turner to have a "dinosaur-like jawbone, tail, and underbelly". It has scales on its back and on its tail, and it usually stands upright. It resembles a small, bipedal Stegosaurus.
The Pollywollyoptasaurus was featured in the episode, "Transparents!", where Timmy Turner brought it as a show-and-tell project to school. The long extinct dinosaur could have only been brought back to life by fairy godparents, something that Timmy's teacher Mr. Crocker quickly and correctly deduces himself based on his own obsessions with fairies. The dinosaur spits up green goo into Timmy's face, and later Mr. Crocker's face, and then manages to run out into the hall in school.
Timmy has Chester and A.J. hunt down the dinosaur before Crocker can find it and use it to prove Timmy has fairies. Chester and A.J. are also approached by Crocker who attempts to sway them with promises of power should he acquire a fairy, but after they manage to capture the dinosaur, Chester and A.J. still decide to side with Timmy instead. However, Crocker steals the box containing the dinosaur away from Timmy anyway, but Timmy wishes the Pollywollyoptasaurus away before Crocker can open the box. When the box is opened, Francis's dog Mange in a Pollywollyoptasaurus mask hops out and bites Crocker's leg. Timmy then got detention by Waxelplax for faking his show and tell (the apparent alive Pollywollyoptasaurus he showed in class since it was seemingly revealed that it was Mange in a dinosaur mask).