Credit: Jamie Chung's Instagram/Jason Merritt/Getty Images

Just in case you were wondering, the cast of Pretty Little Liars really is the best. But even though they’re besties now, there was a time when these little liars were all strangers, and recently, Troian Bellisario revealed that the first time she met co-star Ian Harding, the two got into a fight. Say what?! (Don't worry, PLL fans. It's all water under the bridge now!)

“I got into a huge fight with Ian,” Troian told Good Morning America’s Rachel Smith during the Pretty Little Liars Facebook Live chat with the Liars. “He just annoyed me.”

Whoa! So what was it that set Troian off? You might be surprised to hear their spat started over biology. (Edward and Bella 2.0, perhaps?) Apparently, Ian told Troian he was into biology, but then he proceeded to say something about evolution that Troian — who got a five on her AP Biology exam — didn’t quite agree with. Needless to say, Ian didn’t appreciate her input. 

Thankfully, Troian and Ian were able to put their evolutionary ideologies aside and work together on Pretty Little Liars. And although these two opinionated smarties don’t have that many scenes together, we’re glad to see they’re now besties behind the scenes.

Are you surprised by Troian and Ian’s first encounter? Sound off in the comments!

Catch the Pretty Little Liars Season 4 Halloween special on Tuesday, October 22, 2013 at 8 p.m. ET on ABC Family, followed by the series premiere of Ravenswood!

Crystal Bell is an editor at Wetpaint Entertainment and our resident fan-girl for all things Pretty Little Liars. Follow her on Twitter and Google+!