Doonesbury by Garry Trudeau for May 31, 1976
Transcript:
Man: Hi. Can I help you? Clyde: Yeah, man, I'm a canvasser, workin' for Ginny Slade, see... Man: Ginny Slade? I've never heard of her! Ginny: She's never heard of you either, man, but she needs your help! Man: Hee, hee! What is it really, son, magazine subscriptions? Clyde: No, cookies.
Clyde does start selling cookies much later on.