Ewell appeared in the first season as Vicki, but her character was staked and killed by Stefan (Paul Wesley) after she turned into a vampire.
In the recent second season finale, Vicki and Anna (Malese Jow), who also died in the first season, appeared to Jeremy (Steven R. McQueen) after he was brought back from the dead.
Ewell has now told TV Line that it was a "wonderful surprise" to be offered a return, but admitted that she initially thought it was a prank as the proposal was made on April 1.
"It was crazy to get that script and read it," she said. "I was just as shocked as all of the viewers were."
Ewell added that it was difficult trying to figure out how to play Vicki, as it was not completely clear what was happening in the scene.
"It definitely took me a second to figure out what I wanted to do," she said. "I had a bunch of options in my head, and the one that I ultimately decided on I'd like to keep to myself, just so I can wait and see if it comes true or not! One of the things that makes our job as an actress so fun is that we're able to explore and create something out of nothing - which is essentially what we had to do. It was challenging, but also really fun at the same time."
Ewell also revealed that she would love to have more appearances in the third season, saying: "If they ever asked me back, I would do it in a second. I love the character Vicki so much, I would hope they'd want me back. But that's what makes the show so great, we never know what's going to happen."
> 'Vampire Diaries' season three about Damon, Elena