'Damages' actor Derek Webster replaces Joseph C. Phillips in 'Castle.' Webster will replace 'General Hospital' star Phillips as Robert Weldon, the show's New York City mayor. The producers will delve into Weldon's backstory and his friendship with Nathan Fillion's character Castle. Webster is set to make his debut in early 2012.

http://www.aoltv.com/2011/11/14/kelsey-grammer-returning-to-30-rock/