Honorary Mention: Peter Parker, That Little Nerd From Earth-199999

Earth:… 199999
Tom Holland’s Spider-Man doesn’t appear alongside his other theatrical counterparts in Across, but he gets a referential drop alongside Benedict Cumberbatch’s Doctor Strange early on in the film, as an exasperated Miguel explains to Gwen that his job is to stop disruptions to the multiverse like the one she and Miles witnessed in Into the Spider-Verse… and the one this Peter made during Spider-Man: No Way Home. Maybe they’re saving him for an actual appearance to give Miguel another rage-induced hernia in Beyond the Spider-Verse next year?