Tonight marks the 100th episode of Fox’s “Bones,” which may amaze those who originally only saw the series as something for David Boreanaz to do until Joss Whedon finally got around to making an “Angel” movie. Instead, the show has gradually found a sizable fan base who love the patter between Boreanaz and his co-star, Emily Deschanel, as FBI Agent Seely Booth and forensic anthropologist Dr. Temperance “Bones” Brennan.

Sorry, did I say “patter”? Obviously, I meant “sexual tension.”

This evening’s episode is a flashback to the very first case worked together by Booth and Brennan, one which took place a year prior to the events seen in the show’s pilot. In addition to the fact that it provides an opportunity for the actors to revisit the way they played their characters five years ago (or, in the case of Eric Millegan, an opportunity to play Dr. Zach Addy again period), there’s a concluding moment which has the potential to completely change one of the fans’ favorite parts of the show…or, at the very least, shake it up a bit. My wife, who has seen every episode of the series since its premiere, got a bit emotional at the concluding scene. I’ll be interested to find out if you react the same way.

I was fortunate enough to attend a “Bones” breakfast during Fox’s day of the Winter 2010 TCA Press Tour, and both David Boreanaz and Emily Deschanel were in attendance. Unfortunately, however, my conversation with David was precisely two questions long, thanks to a strange moment where I asked him about working with Diedrich Bader – he plays FBI Agent Andrew Hacker – and got a blank stare and an assurance that he had absolutely no idea who that was.

At the time, I was concerned that I’d gotten bad information, but, no, he definitely had worked with Bader. Weird. Fortunately, before that confusion caused the chat to come to a complete and total standstill, leading someone else to pick up the reigns of the conversation and run with them, I’d asked him how he felt about his series making it to the vaunted 100-episode mark.

“It’s kind of hard to believe that you’re there,” Boreanaz admitted, “especially when it’s hard enough to get a pilot made, let alone picked up. I’ve always maintained that whatever you’re working on, you should work just really in the moment and not think about the next episode. You should just maintain a real strong sense of your work and your ethics and being honest with yourself and just continue to work hard and see where that takes you, whether you do 12 episodes, 20 episodes, or whether you just do a pilot. You’re just fortunate to be working.”

Thankfully, I made no such faux pas while talking to Emily, who was glad to answer my question about how she thinks the character of Brennan has changed over the course of 100 episodes.

“You know, I recently just watched the pilot again, because I’ve been thinking about doing this 100th episode and doing a flashback, so I’ve been thinking about that a lot,” she said. “I think she’s become less guarded, more open…she’s trying to learn socially how to interact with people. Watching the pilot, I was, like, ‘She’s very wild, in a way.’ She’s just determined to do her thing and just does it and doesn’t care what anybody else thinks…and I just love that about her! That’s definitely still true. In one sense, she’s become more polished…and I say that in a lot of ways! But she’s just growing up and kind of thinking about something before she does it. And she’s also trying to understand social interaction and people’s emotions and feelings…and her own! Trying to understand other people’s through exploration of her own. She’s not as quick to just kick someone’s ass! She’s kind of learning to take a breather before she…it’s, like, Fox had this whole campaign of ‘Take a Moment,’ and Brennan had to take a moment before she acted on things. Before, she just acted. That’s not to say that she doesn’t still just act sometimes, but I think that’s a way she’s changed over the years.”

At the time we chatted, they hadn’t yet begun filming the 100th episodes, but they had been having meetings about what it was going to look like.

“Visually, with the hair and make-up and wardrobe, it was fun trying on the wardrobe that was Brennan back in the day,” said Deschanel. “Cynthia Somers, the costume designer, did a great job. She was not there at the beginning, but she did a great job of pulling these things that were very Brennan-esque from the beginning. It’s been great to go and to start thinking about Brennan in that time and what she was. It’s been fun.”