Mr. Kenny Brian Meaner – Mr. Meaner is Jerome Horwitz Elementary School's gym teacher. He is depicted as being an overweight man and with a personality similar to Mr. Krupp's. Like him, he is very cruel to students and often yells at them. He appears in the series, where he is depicted as being incredibly ignorant and talks in a stutter by saying "yeah yeah yeah yeah." In book 12, Meaner becomes Sir Stinks-A-Lot. His name is a pun on the word "misdemeanor" or the saying "can he be meaner." Voiced by David Koechner in the TV series. In the TV series, he has an alternate ego by the name of Sargeant Boxers, which was made as a replacement for Captain Underpants in the first episode of the second season. The Talking Toilets – An army of living toilets created by George and Harold, who were accidentally brought into the real world with a modified photocopier. They could only say "Yum Yum Eat em Up!"

Sir Stinks-A-Lot is one of the few Captain Underpants villains who were able to defeat him, others include the Turbo Toilet 2000 and the Bionic Booger Boy (Minus Carl, Trixie, and Frankenbooger). The permanent maker the kids drew on Mr. Krupp and Mr. Rected's faces resembles Gene Simmons's and Paul Stanley's makeup from KISS. The twelfth installment of the Underpants series, Captain Underpants and the Sensational Saga of Sir Stinks-A-Lot, in which our hero battles the evil, mind-controlling gym teacher Mr. Meaner, comes out on August 25. It’s surprising, simple, and wholly enjoyable. It might not be the best book or the funniest book in the series, but that’s OK, because as it turns out, Stinks-A-Lot is a very important Underpants book. That’s because it’s probably the last one. Milligan, Mercedes (June 20, 2018). "DreamWorks 'Epic Tales of Captain Underpants' Opener Undressed". Animation Magazine.In the Treehouse Comix's version, it is revealed in Book 5 that he is from a planet called Underpanty World. Since the Planet was ending due to the Wedgie Warlords using the giant can of spray starch, his parents named Daddy Long Johns and Princess Pantyhose sent him to earth before the people on the planet perished by the spray starch. Since Mr. Meaner was still a gym teacher at heart evil and ruthless, he didn't care about bringing world peace to humanity or ending world hunger. Mr. Meaner then reflects on how their problems were caused by the students at the school. So he commanded to them that they all return to the school immediately and go about their business as usual, and nothing is to look suspicious. In 2020, ten Dog Man books (including one Cat Kid Comic Club, a spin-off) sold a total of over 3.8 million copies, 13% of the total comic book sales, as charted by BookScan. This does not include digital copies or any copy sold by Scholastic through school book fairs. [8]

This error could be explained by assuming that the staff was transferred from the Piqua State Penitentiary to the Piqua Valley Home for the Reality Challenged sometime between the events of Book 11 and Book 12. In the TV series, Captain Underpants often says "Oooooooo" whenever he finds something surprising or interesting. The Lunch Ladies – The Lunch Ladies are the three women who run the cafeteria. They are notorious for cooking horrible, inedible, and possibly lethal food. They quit in the third book when Mr. Krupp says he cannot punish George and Harold for their antics without proof, though they are possibly rehired after the replacements are revealed to be aliens. Two of the Lunch Ladies are named, Miss Creant, the head lunch lady, and Mrs. DePoint, the cook. The revealed names are puns on the word "Miscreant" and the phrase "Misses the point".

There's something rotten in the state of Ohio, and it's smellier than a pile of putrid gym socks! Steer clear—it's Sir Stinks-A-Lot!

Captain Underpants and the Big, Bad Battle of the Bionic Booger Boy Part 1: The Night of the Nasty Nostril Nuggets (2018) For a kids book, the characters are nicely fleshed out though can be simplistic at times. The main characters here while still being trouble makers never do anything that would really hurt anyone overall. For all the jokes and mischief in it the books especially this volume in the series can still deal with some serious topics. At one point, it is brought up that both kids have ADHD . In most kids books something like this could be a one off mention and then heavily glossed over as being a topic too "mature" for the readers of said book. Here though both of the main characters wear it as a badge of honor instead of something they should be ashamed of. The book also makes some punny references to popular movies, songs, bands etc. Some of which I am not even sure kids are going to get and can be fun for adults reading this if they do.