Flopsy Fish In Yoshi's Island DS in front of Yoshi.
Flopsy Fish are a variety of Cheep-Cheep found in Super Mario World 2: Yoshi's Island and Yoshi's Island DS. They look like Cheep Cheeps but have a couple teeth, jagged fins, and hop out of the water in a curve. They are also more aggressive than a Cheep-Cheep and can be more unpredicatble.
Flopsy Fish also appear in the Island Museum with some Cheep Cheeps.