Castle is not a stripper! He makes this point well known in this preview for the episode "Almost Famous," which centers around the death of a stripper.
Beckett's former partner returns on this episode, while the action takes place at a graveyard. Watch this promo and get excited for "Under the Gun."

Castle Season 3 Quotes

He really is ruggedly handsome.

Ryan (looking at cutout of Castle)

Ryan: (drops egg off desk)
Beckett: Are you guys reenacting the "Humpty Dumpty crime scene?"