Everyone on Earth has suddenly developed really bad breath and Dr. Mu is, of course, to blame. Rufus is transported to a junk asteroid made entirely from rubbish, the Planet Flotsam, where Dr. Mu is extracting the powerful Grot Particle and beaming it across the universe to Earth. Can Rufus stop Dr. Mu before the epidemic of eggy breath reaches toxic levels and the whole planet has to be evacuated?

Desperate to impress his arch-enemy and old school friend Dr. Wu, Dr. Mu decides to steal the sun, using a giant intergalactic space wormhole, a plan that threatens to leave the Earth quite literally out in the cold. Can Rufus save the world from its icy fate? And how on earth is a tin of cat food from his future self ever going to help anybody?

Dr. Mu's latest hair-brained plan is to invade the Earth using pizza. Harvesting the cheese mountains, giant tomatoes and olive groves of Princess Gelina's homeworld, Dr. Mu has built up the biggest pizza chain in the multiverse. And with his profits he is constructing a giant, pizza-shaped starship called the Death Pizza. Can Rufus escape the clutches of Dr. Mu's pizza-troopers, rescue the princess, destroy the Death Pizza and save the Earth? Well, maybe, but only if he can remember the ingredients of a Four Seasons.