A character appearing only in Sonic R, depicted as a floating puppet made in the image of Tails with the addition of a red gem emerging from a wire on the top of its head.
Its only special abilities in the game proper are to hover after a jump (without losing height) for an extended duration compared to other characters and to constantly float (whether standing still or moving) without losing speed or sinking when moving over water. Officially, Dr. Eggman created it with the intent that its doll-like appearance would catch Sonic off guard.
Its blank expression and slow move speed have lent it some popularity in horror memes, including a creepypasta that claims successfully using Tails Doll to win a race against Super Sonic will cause it to attack the player in real life.