Barney Bubble

A Barney Bubble is a round purple creature that spits out bubbles when stepped on in Super Mario World 2: Yoshi's Island. There's two in the game, and they only appear in the Monkey's Favorite Lake level. Licking their bubbles lets you spit out more bubbles. Also, in Super Mario Advance 3, there are two more added in the World 6 Secret, Endless World of Yoshi's.

His name seems to be a take on Barney Rubble of Flintstones fame.