Illustrations and rhyming text reveal the Mighty Underpants War as the true reason dinosaurs are extinct.

When aliens come to Earth, it is for the simple reason that they love to play with and hide in freshly laundered underpants of all shapes and sizes.

"Monsters all over the world have different ways to scare, but they all have one thing in common: they all love zany underpants! And every Saturday night, you will find them in a secret cave, showing off their fancy pants as they dance the Monster Bop! But they have to make it home before the sun comes up--after all, who would be scared of monsters in underpants that are striped and dotted?"--Jacket.