Nathan Fillion Nathan Fillion

This season, Castle will mark the holidays in a big way. "We're planning a Ghostbusters-themed episode to air on Halloween night," reports executive producer Laurie Zaks. Who's she gonna call to offer a guest role? Original Ghostbuster Dan Aykroyd, of course.

The ABC series is also planning its first Christmas episode, a good time for Castle to reunite with his MIA father. "I'm hearing that, too," says star Nathan Fillion. While Castle's mother has claimed she doesn't know the identity of her one-night fling, Nathan believes "she knows who the dad is."

And it looks like Cupid may put in an appearance pre—Valentine's Day, with Ryan (Seamus Dever) and Jenny expected to wed in January. "We always have to do a romantic episode as a tie-in to the return of The Bachelor," explains Seamus, who hints Castle and Esposito may vie for best-man duties. And I'm hearing Jenny may be a bit of a bridezilla.

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