In the Castle season 1 finale, "A Death in the Family" Kate Beckett is devastated when Castle does the one thing she asked him not to do, look into her mother's murder.
Alexis attends her first prom in this episode. That's enough to make any father cry.

Castle Season 1 Episode 10 Quotes

Beckett: (Clears throat) Ahem. What's the deal with men and boobs, anyway?
Castle: Biological. We can't help it.
Beckett: But doesn't it bother you that they're so obviously not real?
Castle: (Pauses) Santa's not real. We still love opening his presents.

Oh somebody's been watching to many Bruckhiemer Films.