Trivia: In Castle's book 'Frozen Heat', there are a pair of homicide detectives named Malcolm and Reynolds, an in-joke to Nathan Fillion's role in Firefly.
Trivia: As a tie-in to the series, shortly after it premiered, ABC began publishing Castle's Nikki Heat books, ghostwritten by a real author and credited to Castle. In 'Heat Rises', a murder victim is mentioned as having owned a copy of the movie 'Air Force One', which was written by "Castle" creator Andrew Marlowe.
Trivia: Nathan Fillion and Darby Stanchfield (Castle's ex-wife Meredith) play husband and wife in the movie Waitress.
Trivia: Nathan Fillion and Stana Katic are close enough in age that "Flowers for Your Grave", the series premiere, aired shortly before he turned 38 and "Crossfire", the series finale, aired shortly after she did.
Answer: The networks are now having winter breaks. A mid season end of new episodes, when they come back after the new year, it picks up as if several months have gone by. Beckett suggested Valentine's Day as a "chick flick" to watch as she is moved in. Also some episodes are not scheduled to air in order.