According to TV Guide, soap opera star Jack Wagner will appear in a January episode of Castle entitled, "Significant Others". He is set to play a former pro golfer named Billy Piper. Piper will become a murder suspect after his ex-wife and a divorce lawyer turn up dead.
Castle has also cast GCB‘s Mark Deklin to appear in "Significant Others", which is currently filming. No news yet as to Dekin's character, but this episode will have several other guest appearances that include: Nancy Lee Grahn~General Hospital and Brendan Ford~Weeds.