Pretty Little Liars
Pretty Little Liars certainly loves to pull a fast one on its followers. Did you catch Jason's sudden change? Alison’s brother Jason was first portrayed by actor Parker Bagley during the first season, but when season two came around he looked quite a lot like Drew Van Acker. His new floppy fringe was different but widely accepted.
Fresh Prince of Bel-Aire
Aunt Vivian is one of the most famous recasts in television history, partially because everyone noticed immediately. The first Aunt Viv, played by Janet Hubert-Whitten, had a big fight with protagonist Will Smith and said "I will never do anything with an assh*le like Will Smith." No surprise that she was then recast. Daphne Maxwell Reid replaced her for the remaining seasons.