Balloon Boo

Balloon Boos are similar relatives to Big Boos that appear only in New Super Mario Bros., encountered in World 4-Ghost House. They are Boos with pink cheeks and their tail is that of a balloon's. When they are not looked at, they will persue the player, while dispensing air, and reduce in size; allowing the player to take advantage to progress. When looked at, they will inflate by inhaling air, gaining size until it has become massive. They will continue to chase Mario or Luigi, even when they have completely yielded all of their air. Balloon Boos can be defeated with a Blue Shell or a Mega Mushroom. They will only attack the player when the Mario Brothers arrive in the same room as of the Balloon Boos.

Trivia

 * When Mega Mario or Mega Luigi collides with a Balloon Boo, they pop and soar away in circles.