Question: who is the first a on pretty little liars?
Answer: Mona Vanderwaal (Janel Parrish) Mona was unmasked as the original “A” in season two and then sent to Radley Sanitarium. She faked her death in season five, but it was later discovered that she was double-crossed by new “A” Charlotte DiLaurentis and held captive in her dollhouse throughout season six.