Cowabunga! is a common Sorcery card from Teenage Mutant Ninja Turtles (TMT), collector number 113. Current market price: $0.18 (foil $0.25), TCGplayer market prices via Scryfall.
Look at the top four cards of your library. You may reveal a Mutant, Ninja, Turtle, or land card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.