So, which episode of the CW drama did Ian have the most fun shooting?
"My favorite scene is from the fifth episode of Season 1, when Vicki and Damon are dancing in the Salvatore mansion and sucking blood out of each other's wrists," Somerhalder told Zap2It. "Kayla Ewell in her underwear for a week was not the worst thing that's ever happened, because she's profoundly beautiful but talented and really giving. It was so much fun."
Ian went on to say the thought of how long they'd been shooting the show made him nostalgic, adding, "I remember Zach Roerig brought this up, when we first got this I said, 'Get ready for the ride of your life.' And it's been exactly that. It's been the ride of our lives. Wow."
Meanwhile, Paul said his favorite moments from the show occurred when Stefan and Klaus revealed they were friends in 1920s Chicago.
"I think there is an unresolved bromance between Stefan and Klaus that I think was cut really short, in my opinion," he said.
"They had really cool stuff in the 1920s flashback and then it just ended. I think they had a really interesting thing going for a minute and for some reason the writers did not want to pursue that."
Nina Dobrev also chimed in about the show's achievement, saying, "It puts things into perspective and it makes you realize how lucky we are."
"It's great to be part of a great show that people actually watch and enjoy and can say that's done this many episodes and is still going. We still, hopefully, have another season in us at least."
The Vampire Diaries 100th episode airs Thursday at 8 p.m. ET on the CW.