Blue Bloods Blue Bloods

On the Blue Bloods set, it's not uncommon to see fake handguns, mock suspect files, claustrophobic interrogation rooms ... and dance numbers?

"We have dance-party Fridays!" Jennifer Esposito tells after grooving and clapping with the crew to Donnie Wahlberg's beatbox tune in between takes. "It's our little way of unwinding as we wrap up [an episode]." She pauses. "We know it's Thursday today!"

Check out photos of the Blue Bloods cast

"It's warm-up Thursdays, dance-party Fridays," Wahlberg explains. "That was just a little taste. We write the music on Thursdays and put on the real show Fridays."Like their dance parties, their show airs Fridays, and this week, fans will meet Esposito's character, Detective Jackie Curatola. Jackie is the new partner of Wahlberg's Danny Reagan, who has had two different partners and worked a case solo in the last three episodes. The third partner may prove to be the charm, partially because the two have been paired before: Jackie and Danny worked narcotics together back in the day."We actually do have a history from way back when," Esposito says. "There's no big introduction. They don't even say how she ended up there. I appear and there I am! I think maybe I wanted to get out of narcotics and he had a position open, and we worked together well before, and that was it. We don't really talk about that, but you can see we have a really great relationship right from the get-go."While Jackie and Danny pick up right where they left off, Esposito and Wahlberg hit it off immediately after meeting each other — a lively, laugh-inducing and, of course, dance-heavy rapport so infectious that you'd never guess that the former Samantha Who? actress has only been on the set "a little over two weeks" and is just filming her second episode.

Blue Bloods' Will Estes: Secret society twist is like The Godfather

"I think I knew him in another life," Esposito says. "We were dancing right away on the first day and everybody seemed really pleased. From what I'm hearing, it does [translate] on-screen. People who've seen the dailies are very happy, so I'm hoping the audience will have as much fun watching us as we do working together."Wahlberg thinks fans will take a liking to Jackie because she "gets [Danny] and his way and reasons for doing things the way he does." In Friday's episode, the duo tries to nab a group of heist men who killed a cop — a case that hits close to home for Danny, as his brother and fellow cop Joe was killed. "It's so early [in their partnership], but you see right away during the case that they understand where they're each coming from," Wahlberg says.That's probably because Jackie is a female version of tough-guy Danny, according to Esposito. Though producers and writers have remained vague about Jackie's backstory and future storylines ("Maybe she was in the Blue Templar too," Esposito jokes), the actress did receive one detail that she's using to shape the "very feisty" Jackie."The one person who described this girl to me said, 'She's not one of these sullen women cops you see on TV. She's really excited to put on a gun and go out and shoot people,'" Esposito says. "Like, she wants to get the bad guys and run around with the boys. That's one of the things I really enjoy. I get a vest and we knock down doors and have shootouts. I like the physical aspect, not just the police jargon. I get to be in the field and do stuff. I want to put someone's head down a toilet bowl! Any time [Wahlberg] gets to do something, I'm like, 'I want to do it too!' He jumped over a car the other day and I was like, 'Hey! I want to jump!'"

Blue Bloods: A cop show — and a family drama

Esposito, 37, who hasn't done a cop drama arc since guest-starring on New York Undercover in 1998, hasn't performed as many stunts yet, but she's looking forward to seeing what's in store — and hopes for a Jackie-centric episode. While Danny's previous partners have come and gone in a blink, Jackie "looks like she's here to stay," says Esposito, who's attached for multiple episodes.And frankly, she wouldn't want to be anywhere else."It shoots in New York! Let's just state that!" she says. "I'm a New Yorker, born and raised, so this is like being at home. To be out on the streets — the city is really a whole other character. This is my dream job — and to work with good people. I love being here. I love working here. And I love our dance parties!"Blue Bloods airs Fridays at 10/9c on CBS.