Considering the incredible hype around American Horror Story: Gaga, should Katy Perry star on American Horror Story S6? I know she's gotten really good feedback for her acting, and I think she'd make for a neat addition to the show. Not to mention it'd be fun to revolve pop girls.
No, since there's never been anything "dark" about her.
Maybe in another series. I can't really imagine her becoming a full actress (maybe an episode here and there, like her ep in HMYM) but if she wanted to something like that she'd be better in a comedy type.
She has been praised for her performance on How I Met Your Mother, though she hasn't gotten an Emmy nomination for it like Gaga inevitably will for AHS: Gaga
I can see her as a clown-type character. Being very colorful and childish, yet she smiles with widened and darkened eyes to reveal that she is actually evil.