T.T.

T.T. is the fastest driver in Diddy Kong Racing. He is also in every level lobby to update you on your total reward information of that particular stage you are at. He has a silver automobile and can be unlocked as a playable character by beating him in every Time Trial race.

Other Games
T.T. may also have been set to make a reappearance in the cancelled game Donkey Kong Racing; as Taj the Genie, a character from Diddy Kong Racing was going to appear in it.

It is unknown if T.T. was going to appear in Diddy Kong Racing's canceled Game Boy Advance sequel, Diddy Kong Pilot as well.

T.T. has been confirmed to appear in Diddy Kong Racing DS in "T.T.'s Wish Tracks" and will be an unlockable character.

Trivia
T.T.'s initials likely stand for either Tick Tock or Time Trial.