The bank teller asked him for identification to prove who he was so he could cash the check. He pulls out a deck of playing cards and shuffles it. He produces one of the king cards and shows it to the teller as if that’s actually him on the card.
Lol! That comic is probably at least 40 years old so it’s probably not for much. You’d think that if he was really a king he wouldn’t have needed to cash a check like that. The silliness of Mad Magazine at it’s best.