"It's a fine fit they do!" the 37-year-old actress gushed to ET's Nischelle Turner on the red carpet.
And though her glam look was on-point, McAdams admitted she hasn’t always felt that way about her style picks. When asked what she would do over if she could manipulate time like Doctor Strange, the seasoned star replied, "Maybe some fashion choices. I was a figure skater so I would probably take back a few of those spandex-y outfits, take away some of the glitter."
McAdams also had an ideal superpower in mind -- invisibility -- but she doesn't mean in a "super creepy" way.
"I would like to be able to go into people's houses and see their decorating," she adorably tells us. "You know, when you're driving at night, and you're looking through the window, and you're like, 'It looks so cozy in there. I wish I could get a free pass to go inside!'"
For more from McAdams' Doctor Strange co-star, Benedict Cumberbatch, watch ET's exclusive interview below!