Smart Ass is a common Creature — Donkey Wizard card from Unhinged (UNH), collector number 45. Current market price: $0.19 (foil $11.99), TCGplayer market prices via Scryfall.
Whenever this creature attacks, choose a card name. If defending player has no cards with the chosen name in their hand, they may reveal their hand. If they don't reveal their hand, this creature can't be blocked this turn.