It's Hilary Duff!
This young mama gave birth to her adorable son, Luca, back in March, but she tweeted a Throwback Thursday photo of her baby bump last week.
It’s hard to believe that she has such a rockin’ post-baby bod now considering how big she was, but this girl’s a trooper — she did star in Cadet Kelly, after all!
But of course, her most iconic role was clumsy teen Lizzie McGuire — who literally had an animated alter ego — on the Disney channel from 2001 to 2004.
Did you know it was Hilary? Tell us below, and then click here to play more “Guess Who?”