The Lucy Show (1962)

S2E19 Ethel Merman and the Boy Scout Show

After Lucy finds out that Ethel Merman and Mr. Mooney concocted a tale to conceal the singer's true identity, she bravely decides to invite Ethel to sing at her son's Boy Scout pageant. Ethel agrees to participate, and the show goes on with Lucy and Mr. Mooney joining her on stage.