The movie stars Kathleen Turner, in a performance that must be seen to be believed. How does she play a 17-year-old? Not by trying to actually look 17, because the movie doesn’t try to pull off that stunt (the convention is that the heroine looks adult to us, but like a teenager to the other characters).
Turner, who is actually 32, plays a teenager by making certain changes in her speech and movement: She talks more impetuously, not waiting for other people to reply, and she walks in that heedless teenage way of those who have not yet stumbled often enough to step carefully.
There is a moment when she throws herself down on her bed, and never mind what she looks like, it feels like a 17-year-old sprawled there. Her performance is a textbook study in body language: She knows that one of the symptoms of growing older is that you arrange your limbs more thoughtfully in repose.
—Roger Ebert, in his 1986 review of Peggy Sue Got Married
Turner discusses her favorite scene in a 1991 interview with Oprah Winfrey