I'd like to be a friend of Castle's. Not necessarily a lover but maybe a woman who's been a constant in his life but who doesn't want anything from him. Maybe we were high school buddies or something?

Like a friend of Becketts and Lanie who would be wanting to hit Beckett with a wet noodle-'Woman, do you not SEE this great guy in front you!'. I'm sure Lanie and I would a good team in our Beckett/Castle hook up. Naturally drooling over 'the catch to be' for Beckett would take up a goodly amount of time over drinks on a Friday night!

I'd be the unknown evil half-sister of Castle, searching out Castle after my father dies. Dad told me, on his death-bed, that Castle is my half-brother. He was married when he was swept off his feet by Martha that one magical night, so they didn't exchange names or numbers. It was before Martha was famous, so it took years before he saw her again and learned her name, and by then Martha and Castle seemed to be doing fine on their own. And he actually loved his wife and stuck with her.

At first I put on the sweet act, charming Castle with stories about our father, but I'm really after his money. Since I'm all alone in the world, I'm allowed to move into a guest room with the Castles, living off him, and thus have a recurring role for about a season or two. Beckett is not blinded by "yay! family!" and starts to grow suspicious of my motives, but since I keep my cool when Castle's around, he takes my side, and I cause some quarrels between them. Eventually I grow impatient and greedy, and Castle realize Beckett was right, and throws me out. I go after Beckett for revenge, but she literally kicks my butt, and I'm out of the series.

I think I'd want to be one of those uniformed officers who hands Beckett a file then walks away.  This would mean I get to spend the day on set with Stana, Nathan, Jon, and Seamus! 

I would love to be a corpse and have everybody peering over me. You know some funny ep where I would be covered by some wierd thing. Castle will make some joke and lanie and kate will roll their eyes. I will try not to laugh and open my eyes!