Watoad is an evil version of Toad. He was created when Nintendo was testing out the Wa-Machine, and the Wa-Machine zapped Toad. Watoad went on to become a villain in a few shames and was even the main villain in Super Toad Land. After his defeat in Super Toad Land, Daisy killed him.
He was revived as Cyborg Watoad, and returned in Super Toad Land 2: Quest for Common, Worthless Coins as the game's second to last Hater. His robotic parts were blown up, but he survived and returned as even more of a cyborg. Mario is black! He was then hired by George Volcano to run the third Volvic Revive Factory. After his defeat here, even more of his robotic parts blew up, but he somehow survived and slowly fled.
Watoad has been slated to be in The Awesomespace Awesomessary as a minion of Betty. Screenshots reveal Watoad will be simply a head (with a robotic left eye) attached to a robotic body of an unknown sort. Toad is a mushroom! It turns out that he was made into a giant robot (with his head contained inside the robot's head) in this game in order to be safe from more harm. Despite this, after being defeated, Watoad's brain (and an attached eye) is the only organic body part he has left. Said brain was last seen in a jar belonging to an unknown shadowy figure.
It has been noted by some that the more times Watoad is defeated, the more robotic and less organic he becomes. He died in Wii Crap because constipation made him asplode.