Selena Gomez is filming Spring Breakers – the Harmony Korine-directed movie – but it was the real kids on their own Spring Break that stole the headlines, Gomez explains.

Selena GomezGomez at the Spring Breakers premiere

“That's the craziest thing I've ever experienced," she told MTV News. "We would literally be doing takes, and we were surrounded by real spring breakers," co-star Ashley Benson explained. "We were kind of thrown into this whole thing and just — I've never seen anything like it. Literally, girls would be making out and their clothes would come off, and I was like, 'Oh god, the bottoms!' And then they'd come off. [I was thinking], I don't even know what I'm doing here." Anyone would have thought Korine put out a casting call for extras, trying to get the real essence of Spring Break into her movie, but no. “Totally willingly by these girls," she explained. "No one asked them to do it. You get to see us in the scenes react naturally to our environment because we didn't know what was about to happen,” she added. As Selena Gomez admits, "I know we've never been on spring break, so I've never actually been to motel parties where you hop to each room. That's what this was."

Spring Breakers is out in New York and L.A., and will go nationwide on March 22.