Dinosaur Neil is the head scientist and tour guide at Dinosaur Grotto. He accidentally ate some experimental dinosaur tissue, which caused him to grow into a great big giant Dinosaur Neil. While not actually turning evil, he just started thinking like a dinosaur, and rampaged through The City, squishing all in his path.
Dinosaur Neil was returned to normal size thanks to The Tick and his sidekick Arthur. Dinosaur Neil is now married to Arthur's sister Dot.