"Big A was never in the pilot. Unfortunately, this means it's a little tougher to narrow down, but this is a person that came into the season a little later. "
"The show's writers decided who Big A was at the end of season two/beginning of season three. And that person may or may not be someone who was at Radley. Remember that Mona started playing the game with a newbie once she was admitted to Radley, so Marlene says it's "maybe" a possibility."
http://www.seventeen.com/celebrity/m...-pll-a-reveal/
But Toby said in an interview that you can figure out who it is from Season 1. So go figure. They might have lied to him? Or thrown in a twin.
Oh and Marlene has annihilated one A possibility... how kind of her. A is not
Paige
.
Link