For the most part, the future of the Marvel Cinematic Universe is shrouded in mystery, largely due to the uncertainty surrounding where Avengers: Infinity War and Avengers 4 will leave the universe and its characters.
But one thing we do know is that the Skrulls - an extra-terrestrial race of shape-shifters - are coming in the near future, leading many to speculate that one (or more) of the MCU's characters has been an alien this whole time.
But who will it be?
Search the Internet long enough and you'll probably be able to find a theory that argues for each one of the Avengers to be revealed as a Skrull, and frankly, it really could be anyone - that's the beauty of this inevitable plot twist. But, for reasons we'll get into shortly, Scarlett Johansson's Black Widow stands out as one of the more likely candidates to be Skrull-ified.
The character's dark past already heightens the air of mystery that surrounds her and when you look at her history in the MCU (and the possibilities surrounding her impending solo movie) the pieces start falling into place.