Keira Knightley, 29, revealed that she took her best friend Emily Hope to senior prom at the Dallas set and angered her teachers when they kissed, ROYGBIV reported.

Hope, who was a model at the time, took the role of the male in the date and showed up at the event wearing a black tie and ripped jeans with Knightley, according to Entertainment Wise.

Hope kissed Knightley when they had their picture taken, which earned them criticism from their teachers.

"One of the teachers took us both aside and said we were never going to come to anything if we didn't know how to dress appropriately for events like that," Knightley said. "So that was my prom. We had a great time!"

A teacher gave them a lecture for not dressing up properly for the event as well.

Knightley said that they both turned up an hour late to prom since she had been filming "Bend It Like Beckham," Pink News reported.

Knightley, who is now married to The Klaxons co-vocalist and keyboardist James Righton, also admitted that she still doesn't feel like an adult up until she has to pay for her bills, Az Central reported.

"I mean, when the tax bills comes in that sorts of does it really and trying to figure that stuff out," Knightley said. "Paying bills, that does it.'

The actress is currently starring in "World War II: The Imitation Game," with Benedict Cumberbatch, Entertainment Wise reported.

The plot revolves around the story of legendary cryptanalyst Alan Turing, who led the team of specialists at Bletchley Park that cracked the secret code of the Nazis.

Cumberbatch will play the role of Alan Turing, and Knightley will portray Joan Clarke, a mathematician who worked alongside Turing during the war to crack the Enigma codes., according to IMDb.

In the movie, which will be released Nov. 14, Turing was jailed after authorities found out that he was homosexual.