Geno (as he appears in Super Mario RPG) is essentially a kid-friendly version of Child's Play he's a possessed doll with a score to settle, except he's on the hero's side, instead of trying to murder innocents and giving me nightmares until my early teens. What's impressive is that this never-before-seen character is one of only FIVE characters you can have in your party, Mario included. Hell, poor Luigi was barely in the game at all. Yet Geno made it in and then promptly disappeared forever, except for a brief cameo in Mario & Luigi: Superstar Saga. The same happened with Mallow, but I think Smash Bros. already met its quota of "fluffy soft pink characters." Unfortunately, Square Enix holds the rights to the original characters created in the game, so we're more likely to see Geno pop up with spiky hair and a zipper-covered outfit in Kingdom Hearts 3 than the new Smash Bros.
Possibly Link's most dangerous and deadly adversary in the character's history the Town Tool Shopkeeper is capable of destroying Link's reputation by having everyone on Koholint Island refer to him as a thief (instead of his name) and can blast Link with a bolt of energy that instantly kills him. Luckily, he's just part of the dream of a giant flying fish that Link somehow wandered into. Still, being even more powerful than Ganon or anything else Link ever faced should earn this shopkeep a place on the Smash Bros. roster.
The truly forgotten damsel in distress even the briefly forgotten Daisy re-emerged as Luigi's amour (taking Mario's hand-me-downs again, even in the girlfriend department) Pauline was briefly getting rescued back when Donkey Kong and Mario not only were enemies, but existed in the same universe. But Donkey Kong started wearing a tie and got his life in order (let's not get into the Cranky Kong thing here), Mario got a blonde sorta-girlfriend, and Pauline got left in the 8-bit dust. She got to re-appear a few times in the "oh yeah, that exists" Mario vs. Donkey Kong series, and theoretically appears in the Super Mario Bros. film as Mario's girlfriend (named Daniella Pauline Verducci in the script). But while Daisy and Peach got to be in Smash Bros., Pauline's stuck being the ex no one wants around anymore.
Reggie has become the face of Nintendo of America from his vaguely unsettling "My body is ready" quote, his extremely-personal Animal Crossing home designs, and his generally outspoken nature have given him a familiarity very few executives have with fans. While Shigeru Miyamoto is unquestionably the more recognizable human face of Nintendo in general, it looks like Reggie could definitely take him in a fight, so if there needed to a real-life person in the game, it would have to be Mr. Fils-Aime. Or maybe they could be an Ice Climbers-esque duo-team (still wearing the winter coats, of course). It might reach a level of meta that would cause the universe to implode, but it'd be worth it.
Thanks to Kevin Allen for his knowledge of Possessed 16-Bit Wooden Doll Copyright Law.