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. Grabbing their bubbles with the tongue lets Yoshi spit out more bubbles. Also, in Super Mario Advance 3, there are two more added in the World 6 Secret, Endless World of Yoshis.

Trivia

 * Its name is a pun on on Barney Rubble of The Flintstones fame.