I'm greatly looking forward to the premiere of WandaVision. It sounded quite
unusual from when Marvel first revealed the show, and the scant details they've
been offering in the lead-up to its launch have done nothing to diminish that
impression. It looks like it will be fun to finally understand what's going on,
though I imagine it will take a while to unravel, and I won't be surprised if
it's a mystery that will span the entire season.
It's an aspect of Scarlet Witch's incredible power, which they barely even acknowledge in the MCU... She's been known to fabricate her own realities from time to time, and AFAIK doesn't need an infinity stone to do it.