Both Mach Rider's identity and gender are ambiguous. They are portrayed with a muscular build, and the NES and Famicom versions' manuals never use any gendered pronouns to refer to them. The arcade port Vs. Mach Rider's stage clear screens slowly introduce piece-by-piece an image of a skimpily-dressed woman (bearing similarities to Jane Fonda's appearance in the 1968 film Barbarella) holding a dagger, but it is never specified if this character is Mach Rider, or one of the other wasteland survivors. However, Mach Rider's trophy description in Super Smash Bros. Melee years later lists them as a male character with he/him pronouns. Even later on, Captain Rainbow, a game centered around obscure and neglected Nintendo heroes, has an unused model for Mach Rider that, while not having visible breasts due to wearing armor, portrays them with a feminine skinny waist.

In a March 2002 Nintendo Dream questionnaire with Mitsuaki Hagishima (the general manager of Nintendo's Planning Department), it was revealed that Banjo & Kazooie were planned to be included in Super Smash Bros. Melee as trophies. However, time constraints and the complexity of the approval process (as Rare, the developers of the Banjo-Kazooie IP, were situated in the UK) led to this being dropped, as well as other Rare associated characters (such as Joanna Dark from Perfect Dark) not appearing in the final game. This was brought up again in a September 2009 issue of Rare's Scribes, where it was mentioned that a lot of Rare character trophies were planned to be included in Melee, but it never happened.