Adrian Pasdar is heading to "Castle".

The "Heroes" star will play an Eric Fallon, an FBI agent who assists the NYPD during a terrorist threat. Look for Pasdar in the Feb. 21 and 28 episodes. [TVLine]

http://www.tvsquad.com/2011/01/10/jessica-walter-to-guest-on-big-bang-theory-dollhouse-star-h/