'Pretty Little Liars': Get Inside Mona's Head [Exclusive Video]

Yahoo! TV

It seems like an eternity since "Pretty Little Liars" Season 3 drew to a close and another bunch of mysteries were left unsolved, leaving fans to utterly obsess. The good news is that Season 4 is quickly approaching, but if you can't wait another moment for your "PLL" fix, you're in luck; the Season 3 DVDs will be released on June 4. As well as the exciting and often chilling episodes of "Pretty Little Liars," the box set includes bonus footage and insider info from the cast and crew! Let's be honest, we've always wondered how Mona Vanderwaal's (Janel Parrish) mind works, and our exclusive sneak peek at the Season 3 DVDs kicks off this conversation. It's Mona's world; we're just scared to live in it.

[Related: 'Pretty Little Liars' Star Sasha Pieterse Shares 5 Juicy Bits on Season 4]

Mona quickly became one of the creepiest characters on "Pretty Little Liars," and this clip reveals that Parrish had originally signed up for only one episode. "I didn't find out until we shot the finale that I was going to be A," Parrish says. Amazing how she went from a single appearance to a show regular — and such an integral one! Parrish was hoping it would play out that way, though, since Mona was A in the books.

[Related: 'Pretty Little Liars' Spinoff 'Ravenswood' Adds Brett Dier and Elizabeth Whitson]

Show creator and producer I. Marlene King goes on to explain the inner workings of Mona's sick mind: "As the game went along and she realized how powerful she felt manipulating these girls, then she became darker and darker, and more obsessed with the game ... and the stakes got higher." Mona's rapid change from geek to cool girl to twisted tormentor fascinated fans, and these DVD extras are sure to give major insight into how the show's writers sculpted Mona's mentality.

Emily and Hanna discuss Mona: 

"Pretty Little Liars: The Complete Third Season" will be available Tuesday, 6/4, and "Pretty Little Liars" Season 4 begins Tuesday, 6/11 on ABC Family.