Sonic Adventure DX Director's Cut Cheats

unlock 2 player mode
Once you beat sonic's story mode, go back and play any level with tails again. Before the level starts, plug in a second controller and have someone holding it. When the level starts, if the second player moves the joystick or presses any button, you'll notice tails correspond to what you just did! That means that if someone's playing a sonic level, the second player can race against you as tails!!!

Note: Since playing as tails is only a small little bonus part in Sonic's game, it'll only show one big screen instead of splitting the screen for both the characters. It's still pretty cool, huh?