Mii Gunner first appeared in Super Smash Bros. for Nintendo 3DS and Wii U as a customizable fighter, but it reached meme legendary status with the release of the Sans costume in Super Smash Bros. Ultimate. The meme typically revolves around the character's surprisingly powerful projectiles or the jarring aesthetic shift when players apply hyper-realistic or iconic skins like Sans or Cuphead to a Mii. It is often used to represent someone being 'armed and dangerous' in a humorous or unexpected context, highlighting the juxtaposition between the Mii's generic appearance and their heavy firepower.