Kathryn Hahn knows not to provide spoilers for her coven. 

The Thurston CarteAgatha All Along star revealed that her son Leonard Henry, 16, and daughter Mae Marie, 15—who she shares with husband of 22 years Ethan Sandler—were only impressed by her role as Agatha Harkness in WandaVision because she managed to stay pretty tight-lipped on the Disney+ series' twists. 

"We watched WandaVision as a family together, and I didn't spoil a thing because I was so paranoid," Kathryn told E! News in an exclusive interview airing Sept. 3. "So, we were all able to see the reveal and the story as it unfolded together, and it was very fun to see them legitimately psyched."

And playing the powerful witch in both WandaVision and the forthcoming spinoff Agatha All Along isn't the only way the 51-year-old scores cool points with her kids. Mae also gets excited when Kathryn steps out for star-studded occasions. In fact, the Step Brothers actress recalled the teen being particularly "proud" of a recent Hollywood event she attended. 

"My daughter was very impressed," Kathryn said before quipping, "And then she was like, 'Did you meet The Rock?' That was her second question."

As for her son? Kathryn admitted that Leonard can be a bit more difficult to please. 

"My son acts like he doesn't think it's cool," she shared. "He'll just walk by the TV like 'Mm,' but I know he thinks it's cool." (For more from Kathryn, tune in to E! News tonight, Sept. 3 at 11 p.m.)

Whether her children are fans of her Marvel character or not, Kathryn knew immediately that she wanted to take a break from her usual comedic acting and join the comic book universe, recalling that the studio "had her at the word 'witch.'"

As she put it, "Having nefarious kinds of intentions is really fun, and being able to do things that I don't necessarily do in my real life." 

Kathryn added, "And just the scale of her, the power of her—just taking up that much space is so fun." 

Agatha All Along premieres on Disney+ Sept. 18.  

— Reporting by Alex Cramer

For the latest breaking news updates, click here to download the E! News App