P Balloon

P-Balloons are power-ups in the Super Mario Bros. series, first appearing in Super Mario World. When collected, they usually make the player to inflate by a lengthy period of time.

Super Mario 64 Manifestation
P-Balloons can be found in some personalized copies of Super Mario 64, despite not being in standard copies. They function similarly to the Power Flowers when mario collects, usually make the player to inflate by a lengthy period of time, similarly to it's functionality in Super Mario World.

It is theorized that the P-Balloon is a remnant of Super Mario FX, which would have supposedly been very similar to Super Mario World. It is currently unknown if this is true.

Trivia

 * In Super Mario 64 DS, when Mario collects the Power Flower, Mario inflates by a lenghty period of time.