Waluigi is Wario's brother. He invented the toilet, the egg drop, the milkshake, the computer, the bomb (Oh, wait, that was Morshu), the sink, the shower, the bath tub, the car, the bike, the motorcycle, the four-wheeler, the eighteen-wheeler, the 9,000!!!!-wheeler, the water balloon, the pie, the Cheese Egg, the teleporter machine, the fridge, the cloning machine, and the boot.
Some people believe that Waluigi is an alien from Planet Waffle sent to steal our cheese and experiment on it so they can win the war against Planet Cheese. However, this is ridiculous as there is no war between Planet Cheese and Planet Waffle, and the three people who believe this are insane.