Uncle Max was Calvin's uncle. He is the oldeer brother of Calvin's father, and brother in law of Calvin's Motheras they looked much alike. He visited Calvin's family briefly and only once, and Calvin very much took a liking to him. Calvin also asked if uncle max was in jail before because he had never seen him before.Calvins Fatherreplied: "Now, now, with Max thats not a bad guess. Hinting that Max may have done something illeagal in the past. He was more mischevious when he was around but it didn't seem to bother Uncle Max. As he left, he offered to let Calvin come visit. Calvin attempted to take him up on his offer immediately. However it wasn't such a bright idea to his parents.
Uncle Max appeared in a week's worth of strips, but did not appear again. Bill Watterson stated in the Tenth Anniversary Collection that Max did not work as a character because he could not address Calvin's parents by their real names because he wanted to refer to them as only Calvin's Parents.