The original pilot script for Castle had a scene with several people playing poker and Steve was one of them. They hadn't asked permission before doing so and later changed it to someone else after he found out through the grapevine.
That's interesting. It's understandable... His (or his look-alike's) appearance would have been like an endorsement and there was no way SK could have known the show would be as good as it is. I guess there were no hard feelings... when SK is mentioned in the show, it's respectful.