In Mr. Funny Upsets Mr. Fussy by Roger Hargreaves, Mr. Funny and Mr. Fussy—two completely opposite characters—have an amusing clash of personalities. Mr. Fussy is known for his love of order, cleanliness, and everything being just right, while Mr. Funny is all about silliness, jokes, and doing things in the quirkiest way possible. When Mr. Funny arrives at Mr. Fussy's home, his antics and playful nature turn Mr. Fussy's perfectly organized world upside down.

Through funny scenarios and illustrations, the book explores how people with different personalities can clash, but also learn to appreciate each other’s uniqueness. It’s a lighthearted, humorous story that encourages young readers to embrace and even enjoy differences in others. Like the rest of the Mr. Men books, it’s simple, engaging, and full of whimsical fun.