Balloony is a green balloon filled, apparently, with air. He can move around quickly by letting out air, but it leaves him deflated. Not a good look for a balloon. Like all balloons, it's important for Balloony to avoid sharp objects and being over inflated.
Balloony’s often a generally kind person, but doesn’t like taking attitude from others, or dealing with people who are too demanding or controlling.

Fun fact: Balloony tried filling himself with helium just once. It was very painful.