Calvin's "Uncle" Max appeared in a series of strips in January 1988, conning the family. Uncle Max is Calvin's father's "big brother", which becomes questionable, as his dad did not know his brother and just met him. Like typical brothers, they often poke each other. When Calvin (who first suspected he was a con man trying to swindle them) guesses that Max was in jail (to explain why he hasn't met Max), his mother is outraged, while his father seems to agree with Calvin, saying " That's a guess". He seems to be a lot smarter and up to date than Mom and Dad, and is more in tune to to musical interests. He is the only good singer in the family. He seems to have a bumpy relationship with children and does not take Calvin's jokes literally, which is the main reason why Calvin and Hobbes dislike him. Max says he is not married (he has 3 girlfriends along with a wife) and does not appear very wealthy. He seems like he has a very attentive "job" which may explain why he left so early. He does not think Calvin's special pills do enough to control him. When Calvin snuck into Max's suitcase to try to find some drugs, Max, annoyed, asks, "Did Mommy and Daddy raise you, or did they just untie you from the stake for this visit?"
Watterson had said Uncle Max was intended to be an expressionist character and include him in further strips such as where the family would go to Max's mobile home. He never appeared again after the week wherein he was featured in the strips, because Ms. Wormwood, Calvin's psychiatrist felt in the end that Max was not a good role model. A substantial reason for this was that it was strange for Max to be unable to refer to the parents with proper names, as he doesn't know they don't have any, and that his drugs didn't help Calvin in any way. This may also explain why none of Calvin's other "relatives" appear in the strip.
When Max asks Calvin if he has kids, he says, "No, I'm six years old!". Max replies to this, saying, "...What difference does that make?".
He somewhat resembles Sadam Hussein. He has a funny accent. Calvin's dad says the reason for this is because he thinks he is of Russian descent. Over the years, "Max" has been discovered to be Hussein.