Michael Sheen has been cast as William Masters in the new Showtime drama Masters of Sex.  Lizzy Caplan has also been cast as his on-screen cohort. From TV Line:

Michael Sheen and Lizzy Caplan are the new Masters of Sex.

Showtime has tapped the pair to headline its drama pilot based on 1960′s human sexuality pioneers William Masters and Virginia Johnson.

The project is based on Masters of Sex: The Life and Times of William Masters and Virginia Johnson, The Couple Who Taught America How to Love, Thomas Maier’s book about the 1960s human sexuality pioneers.