No bride wants a wedding crasher. But when it’s Katy Perry? You just yell and go along for the sweet ride.

Perry, in St. Louis over the weekend with her “Witness” tour, crashed a wedding at the Four Seasons Hotel St. Louis where she was staying.

It had been a beautiful, elegant affair for Hayley Rosenblum, Blonie Dudney and their 300 or so guests.

Around 11:30 p.m., guest Amy Prada was on the packed dance floor when “all of a sudden a huge group of people came rushing in and they were wearing shorts and T-shirts and jeans and hoodies. They were not dressed in wedding attire.”

Everyone kind of stopped to check out the interlopers, who rushed onto the dance floor with their hands in the air, yelling, Prada said.

And then Perry appeared.

Prada grabbed her friend, the bride, and “kind of threw her into the middle of the circle. She was like: ‘What’s going on? This is crazy!'”

Rosenblum and her new husband didn’t mind the intrusion at all, and neither did the guests. Perry and her crew stayed for about 10 minutes, but a couple of dancers stayed to dance longer, Prada said.

“It made the night,” said Prada. “The wedding itself was just absolutely stunning, and the bride was beautiful. But that was the icing on the cake.”

Perry must love wedding cake, because this isn’t the first time she’s crashed a stranger’s wedding festivities.

In 2013 she and “Twilight” star Robert Pattinson were spotted scoping out a wedding rehearsal at a ranch in Montecito, Calif.