Principal Wesley Nichols, often referred to as Big Guy or Big Kahuna by Nate Wright, is the principal of P.S. 38. He is rather obese and is subject to continuous jokes by Nate, 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 and even popcorn. 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.
He once mentioned that he read a lot of comics when he was a kid, and that he had every "Archie" comic.
In Big Nate In A Class By Himself, Nate body slammed him while doing a race to the flagpole with Francis and Teddy, though Nichols had a reason to give Nate a detention, 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 African American or Latino 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 says he is "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. Nate even managed to hack into the PA system so that it would play Mr. Nichols singing karaoke (the song being "The Joker").
- His childhood dream was to be an astronaut.
- He buys a Butterfinger from the vending machine every morning.
- He has a cot in his office for "power naps".