The Grey's Anatomy beauty was tormented by her classmates for not developing like other curvy girls her age.
Walsh didn't stand for the teasing - and fought her bullies until they stopped making fun of her.
She says, "I had problems. I would sometimes get in fights. I would beat up boys. There was a phase (when) they used to call me 'flat chest'. It used to be a thing: 'Katie Walsh is flat-chested!' And I (told bullies), 'You're on my list.'"
But Walsh insists her mean streak has died down.
She laughs, "That's one of the most embarrassing stories of my life... I have a problem with man-violence."