If you're wondering how long creators of The Vampire Diaries have been planning on Thursday's shocking season finale, in which — SPOILER ALERT! — Elena (played by Nina Dobrev) transitions from human to vampire, executive producer Julie Plec has the answer.

"The ending had been in the works for about two years," Plec told EW.com. "In the first series of books, that’s what happens to her. When Kevin [Williamson] and I first came on the show, we said, “Well, it can’t happen to her the way it happens in the books,” which is on, like, page 200 of the first book.That felt obviously too soon, and rushed, and we didn’t want to make a show about a teenage girl who instantly becomes a vampire. But we always knew that her journey would take her there eventually, and we just kept riding the wave of when it felt right."

Plec also gave out hints about the effects Elena's transition will have on next season — specifically, how it will unsettle what viewers think they already know about The Vampire Diaries universe. "If there’s one thing that everyone knows about our vampire rules it’s that when you die and are in transition, your memories start to come back," Plec said. "So, there’s some new information that will be introduced to Elena in the first episode of next season. I think it’s just all part of the ongoing friendship and romantic entanglement that Elena has with Damon."

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