Super Smash Bros Project

Released sometime in 1984 is Vs Urban Champion, one of the first of Nintendo's Vs arcade games, where they put out games running on NES hardware out into the arcade. It's 21a because while I still want to go through it, it technically does not count towards the project, and it'll be the first of many such letters. Urban Champion itself was referenced in Brawl as part of the Famicom Medley, and in Ultimate as a spirit.