This just in, from the Hollywood Reporter:
"Tim Daly is set to guest star in the 'enhanced' two-hour episode of ABC's Grey's Anatomy.... According to the breakdown, Daly's character is described as 'handsome, sincere, like a McDreamy.'"
Paul Adelstein (Prison Break's Agent Kellerman) also has been set to guest star in the episode, with an eye to costar on the potential Addison-centric spinoff toplined by Kate Walsh.
Kate Burton, Grey's Anatomy, and Camille Gauty, Prison Break, have joined Fox's Supreme Courtships, playing a justice and her ambitious clerk, respectively.