There was a joke about a rival Geno that I really didn't have the opportunity to present, and I'm glad (yet sad) that no one thought of it yet.
His name could be:
Geno Black.
I'm sorry.
I find this character concept sick though. Well, I'd say let's run with the concept of this doll being made by the creator of Geno, the doll, as a nemesis-type character. Since the Geno doll is considered to be the hero, then this doll was made to be the villain.
Other name suggestions I had are:
Diavolo, which is the Italian word for Devil.
Dopple, since he vaguely resembles Geno.
Or even Nette. Like "Marionette" but without "Mario", eh, eh? It's like a puppet (like Geno)... but
without Mario. And it has an irony to it since marionettes have strings held by a puppet master, but he doesn't serve the higher authority. He's got no strings to hold him—*gets shot*
I'm not so keen on him being named Gepetto, as the story of Pinocchio details the maker of the puppet be Gepetto. Perhaps the maker of the dolls is a Toad named... Gepettoad.
Regardless, "Xeno" as I'll dub him currently, probably specializes in his arms shifting into melee weapons (as evidenced by the sword in the art), since Geno's arms shift into ranged weapons.
He disagrees with the concept of the stars granting wishes, and rebels against the higher authority. He would also probably believe that the things that are prevented due to wishes should happen anyway. One of those things, apparently, is Mario rescuing Peach from Bowser (which might be noted as one of the most common wishes upon the stars). Xeno makes his way to Bowser's Keep and offers Bowser a chance to defeat Mario. However, all he has to do is destroy the Star Road once again.
Bowser vaguely remembers the concept before Xeno explains that without the Star Road, the wishes that allow Mario to rescue Peach from Bowser's clutches will never be granted. Bowser immediately warms up to the idea, and agrees to work with Xeno. Bowser, with Xeno, ends up destroying the Star Road and scatters the pieces across the world, leaving various baddies in charge of watching over each piece. Bowser then nabs Peach, Mario pursues and fails to stop Bowser. In the clash, Mario encounters Xeno and thinks he looks familiar, but clearly identifies him as an enemy. Xeno reveals that he grows stronger with every wish that goes ungranted, and helps Bowser knock Mario out of the castle.
Mario ends up unconscious in the Forest Maze. Eventually, another star descends to earth and rediscovers the Geno doll and inhabits it. Geno is reborn and ready to undo the actions of his fallen comrade. Without any hesitation, he marches straight to Mario's Pad to recruit the plumber to solve the problem. Of course, Mario isn't there. Luigi IS, however. The two would greet each other, Geno already knows who Luigi is, and Luigi is offered a chance to help both Mario and Geno save the day. Luigi accepts the offer, though reluctantly.
The two rush to Bowser's Keep to try and help Mario, but they're too late. They encounter Bowser and Xeno working as a team. Geno has an encounter with Xeno, each has a moment to reflect their opposing ideals, and Geno and Luigi still lose.
Before this goes on any longer, they retreat, find Mario, yada yada, there's a lot more to this that can be written. Basically, it would be a good way to flesh out Geno in how he reacts to one of his own kind turning to the dark side.
Crapton of potential here, I'd say.