Principal Wesley Nichols, often referred to as the Big Guy or Big Kahuna by Nate, is the principal of P.S. 38. He is rather overweight and is subject to continuous jokes by Nate Wright, although he is very kind to him nevertheless. Principal Nichols is shown to be rather fond of his food, and sometimes Nate catches him eating things like donuts and chocolate bars. In Big Nate: In The Zone, when all the junk food is took out of P.S 38 to be replaced by healthy alternatives, it is Nate who finds soda and unhealthy treats in Principal Nichol's office.
In Big Nate In A Class By Himself, he almost gave Nate a detention for accidentally body slamming him while doing a race to the flagpole with Francis and Teddy, though he said that it was his fault. Later, Nate got a detention during lunch for a "green bean incident". This was when he tried to set a world record for the most green beans eaten in the shortest amount of time. It is shown that he gets out of his office in the mornings only when it is getting painted. When they get together there are no noticeable problems between the two.
He appears to be American, and has a black mustache. He is noticeably overweight.
In the comic strip, Principal Nichols is mostly seen to be wearing a white shirt with black pants and a tie with a checkered coat. When the strip started being colored his tie colors would sometimes change as would his pants. He is also known to wear glasses.
- He has the third-highest rating in Nate's 'P.S. 38 ANGERGRAPH!', rated as 'furious weekly'.
- It is revealed in Big Nate: In The Zone that he has a niece named Noelle Nichols, that attends P.S. 38.
- Most days, he heats up a Cinnabon to eat, as said by Ms. Shipulski.
- Nate usually calls him "morbidly obese".
- He is usually pretty nice to Nate.
- He is usually hit with the worst prank day pranks; once, Nate put Epoxy on his chair and it got stuck on his butt, another time, Nate managed to make his desk disappear, and, at one point, Nate even managed to make his car disappear. Once, Nate even hacked into the PA system so that is would play Mr. Nicholas singing karoke (the song being "The Joker" ).
- His childhood dream was to be an astronaut.
- He buys a Butterfinger from the vending machine every morning