Where you've seen her: She played Donna Pinciotti, the fiery redhead on Fox's "That '70s Show," for eight seasons and Ted Mosby's pretentious college sweetheart in "How I Met Your Mother." Character on this show: Prepon will play blond comedian Chelsea Handler, whose affinity for vodka, her sharp tongue and her few boundaries have caused her escapades to become hilarious fodder in her memoirs. Character similarities: Chelsea is much more outlandish than Donna. But it might be daunting to play a character who is also your real-life costar, since Handler will guest-star as her born-again sister in the NBC comedy. Watch a preview here.
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