The Pipe is a small, white, bent tube with a thick mouth which protrudes from the unlikeliest of surfaces. It is apparently a preferred dwelling place for small Animals.
In Sonic Adventure 2, and its enhanced port Sonic Adventure 2: Battle, Pipes can be found in every Stage. Their purpose is to provide more Animals which they contain within them, though they may also contain bombs. To use a Pipe in gameplay, the player has to press near it, which will make the playable character whistle into it. This will coax the Animal out for the player to collect.