"Things are going to get really tricky (...)" - Julie Plec, Exclusive Interview.

• SPOILER! --> If you haven´t seen Episode 100, 500 Years Of Solitude (#5.11) don´t read this.

Katherine Pierce spent the majority of the episode, "500 Years of Solitude," lying on her deathbed believing her end was near. In celebration of her impending doom, Damon, Stefan and Co. took shots as they reminisced about the terrible things Katherine has done since season one. But after Nadia introduced a Plan B for how Katherine could skirt death, she jumped at the chance. By the end of the hour, Katherine took over Elena's body -- but only Nadia is in on the plan. R.I.P. Elena?

The episode also featured a long list of cameos, listed here in order of appearance:

1. Sheriff Forbes (Marguerite MacIntyre), 
2. Klaus (Joseph Morgan), 
3. Emily Bennett (Bianca Lawson), 
4. Rebekah (Claire Holt), 
5. Aunt Jenna (Sarah Canning), 
6. Uncle John (David Anders), 
7. Elijah (Daniel Gillies), 
8. Vicki (Kayla Ewell), 
9. Tyler (Michael Trevino),
10. Alaric (Matt Davis).

Julie Plec talks to THR about the episode's memorable returns and that shocking Katherine/Elena body-snatch in the final minutes.

The 100th episode featured a ton of cameos, including characters we haven't seen in a while. Since you couldn't feature everyone who made an impact, what were the guidelines with who would appear?

We knew we wanted to bring back everybody that had ever been a series regular for part of our family long-term. On top of that, we just love shouting back to little things, little characters, over the course of the series that were either embedded in the story or had great moments like the Uncle John moment [in season one] or Emily Bennett who, of course, was Katherine's sidekick back in the day.  

The opening was quite comedic, with the major characters reminiscing about Katherine.  How did you want to open this particular episode?

In the beginning, we're reminding the audience that Katherine used to just be a human girl who accidentally got pregnant -- and losing that baby, or having it taken away from her, was the catalyst for the rest of her life and the very thing that turned her into the person that she is. Coming off something so intense and learning that she's going to die, we loved that idea of kicking off the episode with what felt like a celebration.

It was also one of the rare moments where you had a lot of the major players in the same room.

Let me tell you, it takes some time to shoot when you get more than four people in a room too.

We'll get to the big Katherine and Elena twist later, but firstly, when did you cement Klaus and Caroline's hookup in the woods?

We knew that if Klaus had ever left Mystic Falls there was still another chapter of that story to play to really put an ending on their journey -- at least to deliver on their journey. Just because he's on another show, it felt like there was an opportunity for us to add that extra layer that's been missing from their story and we wanted to take it. What better episode to take it than the 100th.

Is there a chance there will be repercussions for Klaus and Caroline's "scandalous sex" or is that your way of closing the door?  

Caroline makes her point very clear and Klaus gives his promise. He fully intends to live up to that promise and Caroline fully intends to move on with her life. I think the consequences will come in the form of how she feels about what she did and what happens if and when other people find out about it.

Is Tyler back in Mystic Falls for good?

He's back and he is a little bit at a loss for who he is and how he fits in and coming off of the experience that he just had, which was very dramatic with Klaus.

Has Damon let go of the power Katherine has over him or will that continue to be an ongoing struggle?

Damon thought he was punishing Katherine because she deserved it and when all is said and done, Damon got a little bit of a lesson in an ugly vengeance and came across the other side realizing that he just needs to let go and move on. Her death gives him that opportunity. Unfortunately, he doesn't realize that she's still kicking, that he's still around to make his life as miserable as ever.

The twist at the end with Katherine assuming Elena's body is a big game-changer. Is Elena gone from the world or will she be back in some form?

All I can say is if Katherine Pierce has her way, Elena Gilbert will never surface again, but it's a little complicated. We'll have to see how it plays out.

Were there other endings or twists you were toying with?  
It became a big reveal about halfway through the first part of our season. Our intention was to say goodbye to Katherine for good but then we realized that Katherine Pierce wouldn't go down without a fight and we have to let her fight for her life 'cause she's above and beyond a survivor.  

What can you tease about what Katherine pretending to be Elena looks like?
If anything has become clear after the last two episodes, is that Katherine wants it all. She wants to be a vampire. She wants a life. She wants her daughter. And she seems to want one of the Salvatore brothers with quite a lot of intention so I think that we'll see Katherine trying to put everything into place so she gets exactly what it is she wants.

How quickly or do the others realize that something is not right with "Elena"?
It will have to wait and see but as we've seen for five years, there's no one better at pretending to be Elena Gilbert than Katherine. Now that she's physically in Elena's body and it's going to be really, really difficult. She's going to have to play the role of her life and she's also very good at it.

Do you have a favorite cameo from the episode?
I love the double whammy of Jenna and Uncle John, which is really a great callback to the beginning of Katherine's role up here in Mystic Fall's in season one and her such dastardly deeds. It was great to get Sarah Canning and David Anders to agree to come back in so that they could celebrate the two traumatic events that got them. [Uncle John's finger chop] will go down in history as one of my favorite moments and surprises of the entire series. It was also celebrating Kevin [Williamson] too. That moment was his epic brainchild.

What are you are looking toward for the remainder of the season and beyond?
We have a lot of stories to tell, which is the good news, so there doesn't need to be an ultimate end date. I think we will keep going as long as we have good stories to tell and as long as people who work on the show want to stay with us and tell us good stories. When the stories start disintegrating into those pitches that we swore we'd never get to unless we were desperate, then we'll try to wrap it up. But those decisions come with a lot of people's input -- a lot of people's opinions so we shall see.

Describe the rest of the season now that Katherine is pretending to be Elena?
Things are going to get really tricky. She's going to shake a lot of things up. She's going to do some damage. It's not going to be pretty, the tornado that is Katherine, but it's going to be a lot of fun.