According to this source – High Fidelity – The top five smartest people in entertainment:
4.) Ellen Muth (Actress) – TV: Dead Like Me – IQ: 156
This up-and-coming star has won a few awards within her career. Although her acting career started at age four, she has received more attention for her recent role in Dead Like Me. She is currently a member of Intertel and Mensa, which has fairly high standards. Mensa requires one to be in the 98th percentile of IQ, while Intertel members must be is the 99th percentile.
Others on list:
Sharon Stone 154/Tarantino 160/Dolph Lundgren 165/James Woods 180, and mentioned in passing Einstein 163/Stephen Hawking 160 although the last two aren’t entertainers by choice.