"It's so much fun because when else would you be able to do something like that?" she said. "I've never had to play a character like that, which is why it was scary at first, but once I started doing it, I love it.
"I never know what I'm doing. I get a script each week and go, 'How am I gonna play this?' And that's fun. It keeps my brain challenged to go to set each day and play with it."
Mona has been seen in different lights on the show. First there was dorky Mona, then popular Mona and now, crazy Mona, who works with "A."
"It's always fun getting to create a new role," she said.
Parrish loves everything about working on "Pretty Little Liars," thought she does have nightmares that one day she'll be on set and forget her lines. Days on the set can be long or short depending on her scene and how long it takes to shoot it.
"Sometimes it can be a few hours, or sometimes it can be all day," she said.
Luckily, Parrish has some great friends to keep her company, like Ashley Benson (Hanna), who she has known for eight years. They have worked together before as have many of the other cast members.
"It's great to be able to have friends on set because you're there for long hours," she said. "We always have a great time."