The Munsters (1964)

S1E18 If a Martian Answers, Hang Up

While experimenting with a ham radio in his grandfather's basement, Herman believes he has made contact with Martians. In reality, he’s chatting with two kids playing with walkie-talkies who are just pretending to be extraterrestrials. They mistakenly assume Herman is just another foolish child, leading to a hilarious misunderstanding as he attempts to impress them with his "alien" conversation.