This volume also picks up on a few loose threads from the previous year, as the mysterious "Poochie" shows up in the flesh; Linus and Lucy's new kid brother "Rerun" makes his first appearance, is almost immediately drafted onto the baseball team (where, thanks to his tiny strike zone, he wins a game), and embarks on his first terrifying journey on the back of his mom's bike; and, in one of Peanuts' oddest recurring storylines, the schoolhouse Sally used to talk to starts talking, or at least thinking, back at her!
The Complete Peanuts 1973-1974 also includes one of the all-time classic Peanuts sequences, in which Charlie Brown's baseball-oriented hallucinations finally manifest themselves in a baseball-shaped rash on his head. Forced to conceal the embarrassing discoloration with a bag worn over his head, Charlie Brown goes to camp as "Mister Sack" and discovers that, shorn of his identity, he's suddenly well liked and successful.