The bullfrog is a frog who only appears in the episode "Rodeo Daze."
The bullfrog is dark green and lime green with tan leopard spots on his back. The frog also has black eyes and appears as a live action frog.
When SpongeBob and the other Bikini Bottomites come to rescue Sandy from the rodeo, they find that Sandy is riding the bullfrog. Once SpongeBob says, "Ahoy Sandy!" this causes Sandy to fall off of the frog, causing Sandy to complain that she "lost the rodeo." After that, Sandy warns SpongeBob that the bullfrog is coming right towards SpongeBob. The bullfrog first attacks the bubble in which the Bikini Bottomites were in, making the bubble pop. Sandy then realizes that the bullfrog now has SpongeBob and lassos SpongeBob directly to her safely, causing the crowd to cheer.