Shirley Henderson will forever be linked to the “ Harry Potter ” franchise thanks to her role as Moaning Myrtle in 2002’s “Harry Potter and the Chamber of Secrets.” It’s a role she landed only after being advised by the movie’s casting director not to mention her age to others. That’s because Henderson was 37 years old auditioning to play a 14-year-old schoolgirl. “The casting director said, ‘Go for it — and don’t mention your age,'” Henderson recalled in an interview with  The Independent . “