13 minutes into this episode, Batman and Robin are asking  the man at the front desk of the Gotham City Museum to close the  museum. Behind Robin is a human figure riding on the back of a  dolphin. This dolphin figure was one of two matching figures that  are seen in The Poseidon Adventure (1972) on each side of the  forward end of the Poseidons ballroom (where the Christmas tree is  located). They sit on a lit up shelf in a recessed area of each  wall.