David Boreanaz

When John Francis Daley was tapped to play a shrink on Fox’s Bones this fall, he had never seen the show, now in its third season.

But after he watched a few episodes, Daley says, he liked the fact that Bones— a comedic drama about an elite team of forensic scientists who solve seemingly unsolvable murder cases — wasn’t strictly a nuts-and-bolts whodunit and that it also went for laughs and romance.

"So many of these procedural shows take themselves so seriously," says the Freaks and Geeks veteran, whose four-episode guest arc as neophyte Dr. Lance Sweets, which began in October, is slated to become permanent.

In tonight’s Christmas-themed episode (8 ET/PT), team partners whom Sweets has been called in to counsel — FBI agent Booth (David Boreanaz) and forensic scientist Brennan (Emily Deschanel) — give Bones fans what they have long been asking for: a first kiss.

Boreanaz, who became one of Bones’ producers this season, says a slow romantic build-up between Booth and Brennan has been intentional. It’s better than "having them start the series by sleeping together and then saying, ’Where do we go from there?’ " Boreanaz says.

"It has taken time for them to get over some obstacles so we can get to some of the crazy stuff," he says. The romantic tension is reminiscent of the ’80s series Moonlighting, leading up to tonight’s kiss. "It gives back to the audience what they have wanted for the past two seasons in a way that is smart and a win-win for everybody."

Says Deschanel: "We kind of get blackmailed into kissing, but we linger maybe a little bit longer than we have to."

What separates Bones from other procedural dramas is the interplay between Booth and Brennan, "about how they get along or don’t get along, the tension that they have between them. It’s a very unpredictable show," she says. "You never know what’s going to happen next."

Tonight’s episode ties together several recurring plotlines that involve Brennan’s long-lost, now-imprisoned ’60s anarchist father, Max (Ryan O’Neal); her fugitive brother, Russ (Loren Dean); and a serial killer who is playing cat-and-mouse with the forensic team.

In that respect, says producer Barry Josephson, it’s a good episode for viewers who have never caught Bones. "This season, the relationships of the characters are progressing."

Although Bones is enjoying its best season ever, drawing 9 million viewers last week, Josephson says it has yet to become a household name, despite a loyal fan base. "We’ve never had the luxury of being scheduled in a place where some enormous lead-in could take us to a bigger rating."

O’Neal says that when he originally read for the part, "I couldn’t make heads or tails" of his role as a dad who abandoned his daughter when she was a teen and has been a fugitive accused of murdering a top FBI official. But as he read more scripts, he noticed that "in a lot of scenes, they talked about the father."

So far, he has appeared in eight episodes and is ready for more.

He loves the recurring role. "It’s the easiest time I have ever had. I guess I was born to play desolate, renegade fathers on the run."