"He stayed in character the whole time and luckily for me, my character was creeped out by him, because I genuinely was at first," the 20-year-old actress said while chatting with David Letterman on Monday's Late Show.
Making the situation all the more uncomfortable was the fact that Gomez didn't even meet Franco until he showed up to film his scenes as a drug-dealing gangster.
"We shot the movie for four weeks, then he came in and walked on set as his character and freaked me out," Gomez continued. "That's who I knew, until we started doing press and I realized he's one of the most intelligent people I've ever met."
She was also quick to add, "He's really nice, I promise. He's great."