Mike Marsland / WireImage 1 / 8
Mike Marsland / WireImage 1 / 8

Well, that didn't go according to plan!

While on the set of "xXx: Return of Xander Cage," Nina Dobrev and Ruby Rose had one heck of a prank war. As they tried to one-up each other and things heated up, Ruby called in the big guns to assist: Taylor Swift. Well, sort of.

OK, it was a Taylor Swift impersonator.

In describing the prank to James Corden, Nina said of Ruby: "She hired a [Taylor] impersonator to come to our set and sing to me and bombard me in my trailer, but what she didn't know was that the girl hired to do this was actually a huge fan."

Nina continued, "She got really nervous and in the middle of it she hit her head and started bleeding."

The impersonator didn't know she was going to perform for the "Vampire Diaries" star until she saw her in the flesh.

"She came in and got nervous and just hit her head," Nina said.

But the prank didn't just cause the impersonator a head injury, it also caused a lot of headaches for Nina and Ruby.

"We had many, many, many, many pranks. By the end of it we were both terrified and we didn't want to leave our trailers," Nina said. "We were quarantined in our trailers because we thought the other one was doing something and plotting against us, which was absolutely right, because we were."

In a separate interview with E!, Ruby said the prank war is fun now, but "it was less fun at the time."

"At one time I had a gorilla-gram stay in my trailer for six hours, but [Nina] would not leave her trailer," Ruby said, adding that Nina somehow knew something shady was going on. "I tried to get her out... Then he had to leave, this poor guy, dressed as a gorilla with these bananas in his hands. I was like, 'Sorry, it didn't work out. Here's your money.' And he went home."