Castle Creator and EP Andrew Marlowe spoil that the show's 100th episode milestone will be classic, charming and surprising. Marlowe reveals the official storyline is still under construction, but will feature "small" call backs to previous seasons and will showcase all their characters in a really great way.
“For episode 100, we didn’t feel like we could do the kind of storytelling that just blows it out because [we had] just done something really huge [two-part event]. So what we’re looking to do is an episode that is a classic, charming, wonderful, surprising Castle episode that’ll be a lot of fun and feature all of our characters in a really great way. As much as our loyal fans would love us to do something out of bounds and crazy, we’re going to do something we think is a lot of fun and a little nod to them and have a chance to play around with the Castle-Beckett relationship in a fun way,” he said.
Marlowe goes on to add: “We were having an over balance of big storytelling in the spring, and we don’t want to let go of the fun and we want to have a good moment with the Castle-Beckett relationship and we’re planning on having something interesting at the end of the season, which is coming up really quickly,” he says. “It’s an episode that is kind of sandwiched in an odd area, so we kind of have to honor the viewing experience.”