Doonesbury by Garry Trudeau for July 31, 1971
Transcript:
Mail room clerk: Geez, that's a big box, Bernie. What's in it? Bernie: Didi, my girlfriend. Clerk: Heh, heh! Sure. That's rich! Bernie: Send it airmail, please. Clerk: Heh, heh. That Bernie, he gets weirder every day...Heh, heh, his girlfriend... Didi: Hey, bub. How 'bout some air holes?
A convict actually tried to escape from prison by mailing himself out!