Characters exuding stereotypical traits of a sexuality, but confirmed to be of a different sexuality entirely

Tink (mewgenics) - Even though he looks and speaks ​like the gayest man alive, Tink has a wife in the game, and Edmund McMillan confirmed on Twitter that he's straight.

Mitch Downe (Paranorman) - The stereotypical jock, who one of the female characters has a crush on, is revealed to be gay and to have a boyfriend.

Also this is not about headcanons, it's about the trope being present in the official media or confirmed by the creators