290 Syndrome

When a developer adds something into their media as canon just because a fandom has theorised it and accepted it as truth before hand.
The name comes from Chapter 290 of My Hero Academia where Dabi is revealed to be Toya Todoroki.

"Hey, did you hear that FNaF 1 canonically happened in 1993?"
"That's 290 syndrome for you, always listening to the theorists"