The Boos are recurring and iconic enemies of the Mario franchise. Tail Boo is much rarer.
Indeed, it appears for the first time in Super Mario 3D Land in 2011, and will not make another appearance to this day, except in a special mode of the game Mario & Luigi: Superstar Saga + Bowser's minions.
Like the classic Boo, it is shy by nature and has the particularity of becoming harmless when the player is in front of it : it hides its eyes, and only attacks when its prey is from behind. The only difference with its counterpart is that it has acquired the specificities of the super leaf: it therefore has a tanooki tail and can use it to attack its opponent.