Doonesbury by Garry Trudeau for May 30, 1978
Transcript:
Voice: Hello? I'd like to speak to "Marvellous" Mark's Dad, please... Man: This is he. Voice: Oh, wow! The kids told me you were on the show, but I didn't believe 'em! Look, I gotta know! What's it like ahving a son who is not only a programming genius, but also one of the top radio personalities of our time? Man: Say what? Mark: Yes, could you repeat the question for those just tuning in?
Fo those scrolling through looking at comments, this is now the correct comic for May 30, 1978.