Mecha Mario

Mecha Mario is a robotic version of Mario, he has not been activated yet

Canon Biography
At some point prior to episode 7, Bowser met a mysterious scientist (though his identity hasn't been officially confirmed, it is obviously Dr. Eggman), who informs Bowser of the Chaos Emeralds. Bowser commissions two secret weapons from the doctor: the Omega Doomship and Mecha Mario. When Bowser learns that Mario is searching for the Chaos Emeralds, he decides to invade the Mushroom Kingdom and kidnap Princess Peach while Mario and his friends are away, in order to hold her as ransom for the emeralds. Bowser then goes to check on the progress of his new weapons: although the Omega Doomship's defense system hasn't yet been installed (Bowser insists on having it launched anyway), Mecha Mario appears to be fully functional.

Fanon Appearences
At the current moment, Mecha Mario is not online.