I just had a little idea. Half related to my edgy sword oc, half related to Geno himself.
So, there's this question we've been asking for a while now... who is Geno? The guy we know and love is a star being, and an agent of the Star Road, of course. But 'Geno' isn't his name, it's the name of the doll that he's possessing, a doll that has to have come from somewhere. Some people have suggested that perhaps he's simply a custom doll that Gaz's mom or someone like that made, but I'm thinking this 'Geno' - whether he's based on some real person somewhere or not - is actually a pretty popular doll.
How do we know this? Well, for one thing, we find upgrades/accessories for the toy literally everywhere the party stops. A whole variety of guns and capes in every major store in town, all in the same consistent style. We even get to see one as far as the Beanbean Kingdom in Superstar Saga. So I'm thinking 'Geno' is a super popular doll that's causing one of those old-school toy crazes in the Mushroom Kingdom and its neighbors. So what if, at some point, we meet the creator of the Geno doll?
Geppetto the dollmaker. A kindly old toad grandpa-type (or whatever species, but I'm picturing a stouter Toadsworth-like guy) who spends his time designing and producing various toys for children. ..Toys that can apparently KO Mario before any star-related magic happens. So maybe he's one of those well-meaning but a little eccentric inventor types, too. I just think it'd be interesting to see where the doll came from, and perhaps some of the creator's related works.
As for my sword doll Geppetto, I'm thinking that when he leaves the Star Road, he needs a proper body to fight in just like Geno did, and he happens to drift down to Dollmaker Geppetto's workshop, where he possesses a prototype successor to the popular 'Geno' figure, a sword-wielding jester. Mister Dollmaker is surprisingly chill about the whole thing and lets the star wander off in the doll - maybe even gives him some other attachments to take with him, not even questioning his motives or plans.
The star obviously ends up communicating with someone at some point, and like Geno he has a name that's utterly alien and unable to be pronounced by non-stars. Annoyed with whoever he's speaking to butchering his name, he tries to think of an alternative. The prototype doll didn't have one yet, so he just thinks back to the old man he met when he first came down and casually lifts his name without a second thought.