"One day she's a little girl wandering the set, and next thing you know, she’s taking over a whole town, mind controlling the citizens to play out her favorite TV Sitcoms! They grow up so fast...," he captioned the pic.
Elizabeth recently spoke to ET about the series, which pays homage to several sitcom formats, and her childhood on the set of Full House with her sisters.
"I have such old, early memories of being on the audience side, and it felt so comfortable," the 32-year-old actress recalled of watching her sisters, who played Michelle Tanner, on the sitcom. "I felt so comfortable as a child. And here I was doing something that felt so foreign as an actor."
She also talked about the "very meta" nod to Full House in WandaVision.
"I was very excited to do it!" she said, noting that Mary-Kate and Ashley, 34, would see and know the reference. "They always watch the [MCU films] that I'm in, which is great."
For more on the Olsens, check out the video below.