Undercover Crocodelf is a common Creature — Elf Crocodile Detective card from Murders at Karlov Manor (MKM), collector number 239. Current market price: $0.08 (foil $0.05), TCGplayer market prices via Scryfall.
Whenever this creature deals combat damage to a player, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Disguise {3}{G/U}{G/U} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)