These days I've been thinking/theorizing "who made the Geno doll?". Thinking on how prior to the doll being possessed, it appeared to already have weapon-like properties (seen when Gaz uses Geno's "ultimate technique" on Mario), such a unique doll must have been made by a talented (if not
genius) toy-maker. Wondering who within the Mushroom Kingdom/Mario Universe could perhaps fit the bill of a master craftsman, or more specifically a toy-maker (or actually, a robotics expert), I thought "what if it was Professor E. Gadd who created the Geno doll?". However, Professor E. Gadd was introduced years after SMRPG, which led me to think "or maybe... E. Gadd's father created the Geno doll".
Here's where my head-canon kicks in with regards to how the Geno doll came to be. Say that, during the time in which the plot of SMRPG took place, a genius craftsman had created his last project; it being a doll that curiously possessed weapon-like applications installed within its figure. However, this doll did not come as a mere epiphany to the master craftsman; it was a request made by a
divine patron. As if foreseeing future events that would eventually come to pass, the craftsman was asked to create a special doll; one that would seem like a toy, but that had practical mechanisms with which to defend itself. Once the doll was complete, the craftsman was to notify this mysterious patron in order for it to pass onto it
something. That "something" was actually a small amount of star energy that would aid
♪!? in the future when it would descend to possess the doll. The energy, once the doll were possessed by the star messenger, would unlock additional tools hidden within its body (Geno's special attacks), as well as allow it to modify certain parts (changing weapons with others that were also requested by the craftsman).