An abbreviation for Time To Penis. Used by game developers and graphic designers as a way to describe how long it will be before the players or users find a way to represent penises in the game. These could either be chat or text descriptions, static images, or even animated penises.
Spore allowed users such total control over their creatures that the TTP was approximately 10 minutes.
According to BackAlleyBrawler, a developer at NCSoft, the ability to rename your character's powers "was quickly rejected due to the 'TTP' factor."