5 Reasons to Watch Castle's 1940s Noir "The Blue Butterfly"

Monday's Castleis taking its characters (and viewers) back in time.

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Nathan FillionStana KaticMark Pellegrino1. Lanie sings! Tamala Jones

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2. The show nails the look and sound of the era. The writers, set-dressers and costumers outdid themselves here, which helps all the characters come alive in the past. From Vera's long gowns and furs to Joe's trench coat and Raymond Chandler dialogue, the show does the genre proud. There may have been one downside, though. "I got to wear a lot of crap in my hair," says Seamus Dever, who plays Detective Ryan. "I had to wash it five times every night to get it out. But it was nice."

3. Speaking of Ryan and Esposito (Jon Huertas)... Castle imagines his other partners in crime-solving as two of Dempsey's thugs. "Esposito and Ryan get to rough Castle up a little bit," Dever teases. Jones says playing characters so different from what the actors are used to is part of the fun of the episode. "If you morphed the Castle characters into the 1947 characters and they're basically playing the same simultaneously, it kind of makes it boring," she says. "What you see, you're going to love."

4. There's a kiss! Actually, there are two kisses. Will it be enough to satisfy the Castle-Beckett 'shippers? "The '40s episode is probably the fulfillment of what most any fan would like to see happen with the Castle and Beckett relationship," Katic tells us. "Fans will be seeing the ultimate expression of love for those two characters."

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5. You can watch (some of) the episode now! Why wait until tonight when you get a taste of the fun now? Check out the video below!

Castle airs Mondays at 10/9c on ABC.