Spoilers for Avengers: Endgame follow below. If you saw Avengers: Endgame and left the movie wondering who in the world Katherine Langford played, you’re not alone. The 13 Reasons Why actress was cast in a key mystery role last October, but ultimately she doesn’t appear in the finished film. And now we know why. Speaking with Josh Horowitz on the HappySadConfused podcast (via /Film), directors Joe and Anthony Russo revealed that Langford did have a major scene in Avengers: Endgame, but the scene ended up being cut. Who did she play? None other than the teenaged version of …