The Cast of AHS...
American Horror Story always has a cycle when it comes to the casts` appearances for each season. Each season the cast change into new characters. Sometimes new people are introduced, some leave, and some come back later on. The actors and actresses who have been in all four seasons are Sarah Paulson, Evan Peters, and Jessica Lange. Actors/actresses who have been in many episodes of AHS are Kathy Bates, Emma Roberts, Frances Conroy, Lily Rabe, Denis O`Hare, and Taissa Farmiga.
http://www.popsugar.com/entertainment/American-Horror-Story-Cast-All-Seasons-32118340#photo-32118340
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http://www.imdb.com/title/tt1844624/fullcredits/
http://www.kichumichu.com/wp-content/uploads/2014/05/Sarah-Paulson-Famous-Hollywood-Actress-Face-Wallpaper.jpg
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http://p1cdn01.thewrap.com/images/2014/06/Taissa-Farmiga_Headshot.jpg
For example, Evan Peters plays as a new person in each season. In season one he plays as a young man named Tate Langdon who`s hiding a secret from himself. In season two he plays as a man who was framed as a serial killer, named Kit Walker. Season 3, he played as Kyle Spencer, a university student who`s life changed from dating a witch. And in season 4 he acted as the rebellious Jimmy Darling, or also called as "lobster boy," since his fingers were conjoined.
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http://americanhorrorstory.wikia.com/wiki/Evan_Peters
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http://americanhorrorstory.wikia.com/wiki/Evan_Peters