Prehistoric Gary is a huge version of Gary and a gastropod seen in the episode: Ugh!. He is extremely large and he is owned by SpongeGar. He is first seen when SpongeGar leaves and says, "Bunooga ready! Tabonga, Gary." Gary doesn't move. SpongeGar says more sternly, "Gary, tabonga!" Gary finally obeys. Squog is very afraid of him. Prehistoric Gary also leaves slime trails everywhere which bugs Squog also. His slime trails is commonly known among the trio as "Tabonga".
Prehistoric Gary basically looks exactly the same as Gary but he is bigger than Gary. The only real difference is that he has spikes coming out from his shell, having a Stegosaurus-like tail, and a thick unibrow. Squog always slides on his Snail Trail and goes round in circles.