Arielle Kebbel , Paul Wesley

In Thursday's episode of The Vampire Diaries (8/7c on the CW), Stefan (Paul Wesley) is marking his 162nd birthday and best bud Lexi (Arielle Kebbel) comes to Mystic Falls to celebrate. While Kebbel (Gilmore Girls) tells TVGuide.com that Lexi is unlike any of the vamps we've seen before — she happens to have a fun and bubbly side — she's still quite dangerous. Damon (Ian Somerhalder) and a few Mystic Falls residents learn that the hard way ...

TVGuide.com: Lexi wasn't a character in the novels. What can you tell us about her?
Arielle Kebbel:
She is about as much fun as anyone who's 300-and-something years old. She's this burst of energy, a complete life force. It's safe to say she's pretty much been everywhere, seen everything, lived every moment and that makes her even stronger, even more confident, even more sarcastic because she has all of this life experience behind her.

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TVGuide.com: How is it like taking on the role of someone who has all this world knowledge?
Kebbel:
It's a lot of responsibility. What seems like simple dialogue — everything is twice as complicated because everything has a double meaning. I'm not playing a high school kid, so watching the different dynamic to how Damon and Stefan react to things to how Elena [Nina Dobrev] reacts to things; they live in completely different worlds. Nothing scares you or affects you in the way that a typical scary situation would. For example, if you're getting hit with bullets ... it doesn't kill you or affect you. How does one react when getting shot with vervain? I had to figure that out and how a certain poison would affect my blood.

TVGuide.com: How did Lexi and Stefan become friends?
Kebbel:
They have been best friends for hundreds of years. [The producers] didn't really want to uncover, in this particular episode, a lot of their past other than you really wanted the audience to feel like these two have been best friends and inseparable through thick and thin. We mention some of our past fun times together, but we don't spend a whole lot of time on that in this episode.

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TVGuide.com: What is the relationship like among Stefan, Damon and Lexi?
Kebbel:
I'm older than both the boys, and although I have unconditional love for Stefan, there's also an unspoken understanding that I'm older, which means I'm more powerful. That comes as a huge threat to Damon, which I love. In a weird way, it forces Stefan to respect me and respect my opinions. I have more power than them, I have more strength, I'm more ferocious and when I turn I'm a force to be reckoned with.

TVGuide.com: Because Lexi is such a strong vampire, does Damon fear her?
Kebbel:
Yeah, he fears her and it pisses him off. She knows it and loves it. She's not scared of him at all and she likes to call him on his B.S. and meet him at his game. She likes to remind him that however evil he thinks he is, I'm still stronger and older and more powerful. I choose not to use my power the way he does because I choose to rise above it, but if push comes to shove, I will use it against him.

TVGuide.com: How does Elena react to having Lexi around?
Kebbel:
I think anytime you first meet a girl in a towel in your ex's house, I think it calls for a very awkward moment, which we definitely have. Towards the end of the episode, Elena and I have an exchange that hopefully will carry through for the next couple of episodes and help her figure some things out about Stefan that I don't think she was able to really hear before.

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TVGuide.com: Does Lexi approve of Elena and Stefan?
Kebbel:
In the beginning, she's pretty freaked out that she looks like Katherine, but we work through that. In the beginning, I don't approve at all. As any best friend would do, once you see two people together and you pick up on what it really is, ultimately you want your friend to be truly happy no matter what. Lexi can tell how special it is, what the two of them have.

TVGuide.com: She may be nice, but all vampires have an evil side. Will we see that come out in Lexi at all?
Kebbel:
You betcha [Laughs]. Let me tell you something, the hours I spent getting red contacts and getting fangs made were all worth it. I got to do some pretty cool and pretty evil stuff in this episode. It's not every day you get to toss around cops [Laughs].

TVGuide.com: Will Lexi be returning to the show?
Kebbel:
I would love to. It's so much fun breaking a fang in Mystic Falls, but we'll have to wait and see. We'll leave that one up to the audience.