Sigmund and the Sea Monsters (1973)

S01E01 The Monster Who Came to Dinner

Johnny and Scott bring Sigmund back from the beach and conceal him in their clubhouse to avoid Zelda, who is preparing to host the sheriff for dinner. Simultaneously, Sigmund's family receives an unexpected visit from their affluent Uncle Siggy, who insists on seeing Sigmund; otherwise, he threatens to cut them out of his will.