Bananawani

Bananawani (called Bananagator in the English dub) are giant crocodiles with a banana-shaped growths on their heads. They are so fierce that they are said to even prey on Sea Kings. Despite their strenght they were easily defeated by Luffy, Zoro and Sanji.

Crocodile seems to have kept many Bananawani as pets and could control them as they were often seen in the room with him and Robin without any sort of aggressive attitude toward either of them back in his old (now destroyed) casino in Rainbase.