Sam, the title character of Sam's Strip, runs the comic strip Sam's Strip and is fully aware of being in the comic strip that he runs. Each strip offers a gag (and the occasional political nod) featuring Sam, his unnamed sidekick (later to be christened Silo in a follow-up series) and cameos from other characters from the world of comics (Blondie, Popeye, Charlie Brown) and fiction (Humpty Dumpty) and real life (Charlie Chaplin). The gags and jokes often challenge the world of comics -- characters know about the conventions of the strip they exist in; all the tropes (gloom clouds, black eyes, sleep logs) of comic strips are available in a cartoon prop closet; there are howlers and groaners, nice and terrible puns, interesting takes on famous jokes and scores of famous names dropped about.
The collection subtitled "The Comic About Comics" offers all the strips along with an introduction and an appendix of notes. Highly recommended.