Why Lady Gaga Slapped Fiancé Taylor Kinney When They First Met

— -- It wasn't love at first sight for Lady Gaga when she met fiancé Taylor Kinney.

The "Chicago Fire" star, 34, told "Watch What Happens Live" host Andy Cohen what happened the first time the couple met on the set of Gaga's "You and I" music video in 2011.

"I show up and they're like, 'Oh this is the idea. This is the idea.' And I go, 'OK, just let me do my thing," Kinney recalled. "And I remember I went up, and we're rolling, and I kissed her and she didn't expect it. They cut, and she slapped me."

Kinney called the moment "awkward."

Fortunately they got past it.

"The next take, I just did it again and then she didn't slap me. She didn't slap me then," he said. "We had a good time. I think there was chemistry."

In fact, the shoot went till about four or five in the morning, after which the pair exchanged contact information.

"A few weeks went by and we kept in touch and then that's that," he said.

The couple got engaged on Valentine's Day, when Kinney proposed to the 29-year-old pop star with a heart-shaped diamond. But they've yet to set a wedding date.

"We’re so busy," Kinney said. "We’ve been engaged for less than a year. So, we’ve been talking about whether it’s New York, Los Angeles, destination place, so we don't have an exact date yet."