Supernatural: Danneel Ackles on filming her first scene with Dean, Sam, and Castiel

Supernatural is no stranger to faith healers. It's also no stranger to women named Jo. But the show is about to introduce a character unlike anyone we've ever met: Sister Jo, played by none other than Danneel Ackles.

Danneel, the real-life wife of Supernatural star Jensen Ackles, joins the series in this week's episode, titled "Devil's Bargain," wherein Sister Jo finds herself making a deal with Lucifer. EW hopped on the phone with Danneel to talk about her decision to join the show and what to expect from Sister Jo.

ENTERTAINMENT WEEKLY: After 13 years, what made you finally want to join in on the fun?

DANNEEL ACKLES: Mostly the character. I haven't acted in a couple years and Eugenie [Ross-Leming], who is Bob Singer's wife and one of the executive producers and writers on the show, wrote this character with her partner, Brad [Buckner], and she called me and she pitched it. [Sister Jo] is such a badass. I was like, "Yeah, this is what I want to do." I didn't want to go on Supernatural and be a love interest of the week or have the guys kill me in some horrific way. But this character, she's just a badass. And where else can you go and bring your kids to work and hand them off to A camera while you're shooting? So it was a no-brainer for me.

Did they write the character with you in mind?

That's what I've been told. They were like, "She's basically you so have fun with it."

All we know about Jo so far is that she's a faith healer. How would you describe her more generally as a person?

She is a businesswoman. She is a legitimate faith healer and a very powerful faith healer, and she loves doing it, but she is a businesswoman first. So she is always looking for: "How much money can I charge this person in this town?" It's all about business for her.

We know she finds herself in a deal with Lucifer. Is this something she enters into willingly?

She's attracted to power, and she, herself, is a very powerful, big personality, and so she initially is very attracted to him because of that. She's like, "Okay, I'm a powerful person, you're a powerful person, let's see if we can work something out that benefits us." So it's not really like she's a good girl or a bad girl; she's about what's going to be best for Sister Jo.

What are her thoughts on the Winchesters?

It goes back to her not really being good or bad. She's just going to do whatever works for her. She's approached by Lucifer and then the Winchesters are attracted to Lucifer—obviously they're looking for him—so they come across Sister Jo, and she is the type of person that could have a lot of deals going at once. They're looking for Lucifer and she's like, "Well, I can help with that." So she's not really loyal to anyone in particular but herself. She is numero uno.

This is obviously a set and crew you've been around for years, but this is your first time acting on this set. Did anything surprise you about the experience?

My first scene that I did—we shoot out of order—the first scene was with Jared [Padalecki] and Jensen [Ackles] and Misha [Collins]. I hadn't worked in like four years and the first thing I had to do was walk into a scene with those goofballs who were looking at this like it was the most surreal thing. The four of us are standing there, all looking at each other like, "This is a weird dream." There was a lot of laughing, which was great. I was nervous that that was the first scene, but looking back on it now, it was just a great way to break the ice and get in. And 40 takes later, we were actually over the fact that it was the four of us and we got on with it. [Laughs] But it was a lot of fun.

So fans can look forward to the gag reel.

Oh, there's a great moment there—a really good one, courtesy of me, take three. There might've been some falling. Something to look out for. [Laughs]

Supernatural airs Thursdays at 8 p.m. ET on The CW.