Both Fox and Marvel partially own the rights to the characters of Quicksilver And Scarlet Witch, which is why they’re both in Avengers: Age of Ultron and we’ve already seen Quicksilver running up walls in the best part of X-Men: Days Of Future Past. Fox can use the characters as long as they don’t mention their role in The Avengers. Marvel can use the characters as long as they don’t mention their father (Magneto) or reference mutants or mutant powers. So how is Marvel going to explain the twins’ powers if they can’t call them mutations?
We’ve speculated that Marvel would re-frame them as members of the Inhumans who gained powers from the Terrigen Mist. Considering Marvel is already incorporating the Inhumans into Agents Of SHIELD, that wasn’t a bad guess. But a prequel comic released this week — a panel from which you can view over at /film or THR — reveals what origin of the twins’ powers the Marvel Cinematic Universe will be using.
The one-shot comic is in canon, and it’s titled Avengers: Age of Ultron Prelude – This Scepter’d Isle. Oof. Quite a title there. Anyway, writer Will Corona Pilgrim explains their powers and ties it back to their post-credits scene in Captain America: The Winter Soldier. io9 summarizes:
Baron Von Strucker has been using Loki’s staff to mess with people and unlock powers within them, which includes Pietro and Wanda. Given that this is pretty much exactly what it looked like when Von Strucker popped up with the twins in the Captain America: The Winter Soldier post-credits scene, I feel a little silly that we all jumped to find more complicated origins when the obvious answer was just right there.
We’ve got a feeling Von Strucker is going to regret poking Scarlet Witch with a Loki stick. You wouldn’t like her when she’s angry.