Most of Us still find it hard to believe that it has been 10 years since Pretty Little Liars finally revealed A's identity. Based on the book series by Sara Shepard, Pretty Little Liars originally aired on Freeform from 2010 to 2017 and followed five best friends who were constantly taunted and treated by an anonymous person named A. The series became a pop culture phenomenon which inspired spinoffs, including Ravenswood, Pretty Little Liars: The Perfectionists and Pretty Little Liars: Original Sin.