The Uranium Unicorns from Uranus Dav Pilkey
Ricky Ricotta loves his Mighty Robot, but sometimes it's hard for a little mouse to have a best friend who's so BIG. One night, Ricky makes a wish: if only his Mighty Robot had another friend who was his own size. Little does Ricky know, his wish is about to come true. Evil Uncle Unicorn has travelled all the way from Uranus with a mean and nasty plan...