But now that the Scarlett Witch and Vision are pregnant, what does it mean? The answer may lie in Marvel comic book history, and it could reveal plans for the studio's next big Avengers crossover movie.
Wanda and Vision's children, explained
In the comics, Wanda and Vision get pregnant through magic — since Vision is a robot, that's seemingly their only option. They have twins named Thomas and William. However, it's eventually revealed that Tommy and Billy were actually created using fragments of the soul of a demon lord named Mephisto. (Yes, this is seriously a thing. Don't believe me, here's proof.) Sadly, Mephisto later decides to reabsorb his soul (so selfish!), which essentially kills Thomas and William.
Wanda doesn't take the loss very well. She teams up with Doctor Doom (the supervillain) and winds up destroying Vision and killing Hawkeye. This all culminates in Marvel's famous House of M plotline, in which the Scarlet Witch uses her powers to rewrite reality and erase all mutants from existence by taking away their powers.
Will House of M happen in WandaVision? Could we even get a reverse House of M where Wanda creates mutants in the Marvel Cinematic Universe instead? Anything is possible, but Wanda and Vision's children could also have another huge implication for the future of the MCU.
WandaVision could set up the next Avengers movie
For now, all we know is that Wanda is pregnant, but there were plenty of clues in the WandaVision trailer to suggest she's having twins. For one thing, the trailer showed Wanda and Vision holding a pair of babies. For another, one teaser shows a fridge with the letters "B" and "T" clearly visible on it. That's got to stand for Billy and Tommy, right?
Here's where things get really interesting. In the comics, years after Wanda's epic rampage, two members of the Young Avengers named Billy Kaplan (Wiccan) and Tommy Shepherd (Speed) figure out that they're actually brothers. What's more, they're the reincarnated versions of Wanda and Vision's children.
If WandaVision decides to follow this thread from the comics all the way to its conclusion, the Disney+ series could be the key to Avengers 5 — assuming the next big crossover movie is all about the Young Avengers.
What's more, the rest of the MCU seems to be moving in this direction as well. The next Ant-Man and the Wasp movie features a recast Cassie Lang (Kathryn Newton), who eventually becomes a superhero in her own right. Meanwhile, the Disney+ Hawkeye show will introduce Kate Bishop (Hailee Steinfeld) as a young hero who takes over for Clint Barton.
All the pieces are there, now Marvel just needs to move them into position. And it looks like WandaVision might be the first major step towards a Young Avengers story in the MCU.
WandaVision is streaming now on Disney+.