Pretty Little Liars

Almost every cast member knew who A was except Lucy Hale. They were afraid she would tell someone else because she's not so good in keeping secrets. She stated that herself in an interview.

Tammin Sursok originally auditioned for the role of Spencer Hastings, but got casted as Jenna Marshall instead

The person who originally played Alison's brother Jason DiLaurentis was Parker Bagley, after season one Drew van Acker took over the part.