Will the best artist win?
The art teacher asks the students of Room 3B to draw posters of things they love, and one of them will get to display his or her artwork on South School's brand-new TV show. Harry doesn't care about the contest. Mary, on the other hand, is convinced that her poster is the best, and she can't wait for her television debut. But if Mary's poster doesn't get selected, then she's going to make horrible trouble for Room 3B—especially...

With Miss Mackle in the hospital, the class isn't in the mood for holiday cheer, so it is up to Harry to put a smile back on Miss Mackle's face and the spirit back in his classroom.

Harry plots revenge against Sidney, the class tattletale, when Miss Mackle's second graders go on a field trip to the pond.

"Best friends Harry and Doug must find their teacher's missing diamond in time for the class talent show."--

"When Harry and his pals in Room 3B aren't invited to their teacher's wedding, they invite themselves, and wind up saving the day"--Provided by publisher.

When the origami pig that Song Lee made for her grandmother is seized by a substitute teacher, the usually well-behaved third-grader breaks a classroom rule to rescue it from the "June box."

A special Valentine's Day card helps third-grader Harry overcome his fear of climbing the rope in gym class.

When Sid, his annoying third-grade classmate, ruins Song Lee's origami praying mantis, Horrible Harry plots triple revenge on the troublemaker.

Harry and his detective classmates try to find clues relating to a mysterious locked closet in Room 3B.

Harry incorporates his fascination with earwigs into Miss Mackle's class project of acting out a fairy tale in front of the other third graders.