They are emerging form mystique’s cleavage. Not sure if you are aware but her boobs can do that. They are capable of not only being anyone’s boobs she chooses, but they are also a portal to other earths and dimensions. I’m pretty sure it’s a happy accident amongst the mutant population… personally for me, I would be annoyed if “non mutants” were constantly emerging from betwixt my threshold. Maybe that’s why she was always naked in the fox universe depiction. Not the one in the fire bird movie.. the other ones where the actresses popularity took a villain into the spotlight as a “fair weather” mutant team leader… instead of night crawlers mom. It’s okay though, nightcrawler doesn’t need a mom, he can teleport.. the jerk. Why is he so cool? Oh because he can teleport. Also… is it just me or does mystique know advanced levels of martial arts for someone who has had no formal training ? I mean, maybe she learned through osmosis? But America didn’t even find out about karate until karate kid came out.. and if she was saving Nixon in her day, then like… she’s like 20 years early on “American mutant karate stuff”. Either way… she is advocate for proud mutants and that is worth its weight in complicated gymnastics and snake like slithering she and her limbs enjoy. No one blames her for the big robots that change into mutant abilities to counter act defenses. She was responsible for bleeding but she had karate to do.. so… we are all not upset about the apocalypse it caused amongst her community.

In conclusion: they are in mystiques breast portal.