Nathan Fillion

Spent last night in Beverly Hills at the Paley Center for Media, which had a screening and panel discussion to celebrate ABC’s comedy-mystery hit "Castle."

The episode shown was the first part of the two-parter — airing Sunday and Monday — featuring guest-star Dana Delany as an FBI agent who helps NYPD Detective Kate Beckett (Stana Katic) and her crimefighting consultant, mystery novelist Richard Castle (Nathan Fillion), track a serial killer obsessed with Nikki Heat, Castle’s fictional character based on Beckett.

Moderator for the evening was "Dancing With the Stars" host Tom Bergeron, who’s guest-starring in an episode of "Castle" called "The Late Shaft" (shooting this week, airing April 12), playing a late-night host, with Fred Willard as his sidekick and Bill Bellamy as his rival.

Bergeron was pretty spoilery about his role on the show (out of respect for those not present, I’ll leave those bits out), but from his detailed questions about "Castle" episodes, he’s either a dedicated fan or was incredibly well-prepped.

I was on set for filming of several of the scenes in part one of the two-part episode and wrote a feature story — watch this space for that later in the week. And, you can click here for a little preview story I did for Zap2it with Delany and Fillion.

The episode was a hoot and delighted the audience (who were pretty pumped to start with), and the panel spanned the "Castle" world with Fillion, Katic, Molly Quinn (who plays Castle’s daughter, Alexis), Susan Sullivan (who plays Castle’s mother, Martha), Jon Huertas and Seamus Dever (who play Beckett’s cop underlings Esposito and Ryan), Tamala Jones (medical examiner Lanie Parish) and Ruben Santiago-Hudson (Capt. Roy Montgomery), show creator Andrew Marlowe and producer/director Rob Bowman.

I did a lot of interviews on set, so expect much "Castle" goodness to roll out in the future.

In the meantime, here are some quippy highlights from the evening ...

Fillion on reading for the role while wearing a pink polo shirt for "Desperate Housewives": "Stop looking. I’m this guy. Ignore this (shirt). I’m really cool."

Quinn on Fillion and Castle: "He’s so much like Castle in real life. Susan’s a little more classy (than Martha)." Sullivan: "I’m more classy."

Dever on Fillion and his "Firefly" character, Mal Reynolds: "’Firefly’ was great, but he’s more fun than that. He’s not a harda—." Fillion: "He’s not a harda—, with a hard a—." Jones: "I have a habit of grabbing Nathan’s butt." Fillion: "What happens in the morgue, stays in the morgue."

Dever on his close relationship with Huerta: "I’m going to help him install his floors next week." Bergeron: "Get a room, you two."

This theme persisted. When a question came up about sexual tension, Marlowe said, "Between Ryan and Esposito?"

More on topic, Marlowe said: "She (Beckett) plays him (Castle) like a fiddle," to which Katic replied, "I think there’s nothing sexier than swordplay." Eyebrows all the way up, Fillion said, "Wow."

Marlowe said that "Castle" hadn’t yet received word on a season-three pickup, but he remained "hopeful."

The conversation turned to Twitter, on which @NathanFillion has well over half a million followers (some of which Jones admitted attempting to poach).

Bergeron commented that he had seen Quinn tweeting in the green room, to which she replied, "That was actually my first tweet!" Quipped Bergeron, "There’s so many lines I won’t use right now." "She’s 16, Tom, 16," cautioned Dever.

Also, as Fillion pointed out, "Castle Twitters, and he follows me."

Sullivan recalled reading for the part, and being a lady "of a certain age," she didn’t want to look down, so she briskly ordered the seated Fillion to rise. That, she said, "got me the part."

Bowman then talked about first recognizing Katic’s acting abilities, "She was throwing it back at Nathan. She had a lot of moxie, great attitude ... we work on that sometimes." Then he admitted, cautiously, that Katic had "more than I expected."

Bergeron complimented Fillion on his girly scream (which can be heard in this Sunday’s two-parter opener), to which Fillion replied, "Turn the hero into a goofy guy and touch the man’s feminine side."

Fillion then recreated the squeal on command.

Talking about her relationship with Fillion, Quinn nearly teared up, saying, "He’s really just like a second dad to me, because my dad’s back in Texas."

Bowman explained how quick pacing and a lot of fast talking allows the show to pack 55 pages of script into 42 minutes of air time. For those not familiar with the length of TV scripts, that’s like stuffing a size 10 foot into a size 8 shoe.

Also on display in the episode are copies of Castle’s newest book, "Heat Wave," which comes out in paperback on July 27. Supposedly the next book is titled "Naked Heat," which caught Katic by surprise (apparently Beckett doesn’t know yet either).