El pedo más grande del mundo is absolutely hilarious. It's about a farting competition between animals in the jungle, and of course it demonstrates that the bigger, stronger creatures are not always better. It manages to be ridiculous and silly and hilarious, without being gross, in spite of the subject matter, and it packs a surprise ending.
Laura du Faÿ, the same illustrator who did ¡Eso no es normal!, did another fabulous job with the artwork.
I highly recommend this book.