Crocodile

Crocodiles are vicious reptiles that can be found on parts of Mushroom World. The Kremlings are a race of advanced crocodiles, but typical crocodiles have made a few appearances throughout the Mario series as well. They mainly appeared in The Super Mario Bros. Super Show! episode "Crocodile Mario", where they were portrayed with voracious appetites, and inhabited Down Under Land.

In "Crocodile Mario", Kangaroo Koopa stole a Magic Statue from a town in Down Under Land that repelled crocodiles. Without the Magic Statue, the crocodiles were free to roam the town. The crocodiles came close to eating everyone there, almost eating the entire general store and the tree that everyone took refuge atop of in the process. Mario and Luigi eventually retrieved the Magic Statue and liberated the town from the crocodiles, who chose to pursue Kangaroo Koopa instead.

As his name implies, Croco is presumably a crocodile of some nature.

Trivia

 * According to Cranky Kong in "Best of Enemies," crocodile eggs make the worst omelettes.
 * Vector the Crocodile is an anthropomorphic crocodile from the Sonic series.