This flash mob was of the whimsical kind

As Jean Smith, 63, arrived at 30th Street Station on a train from Wilmington Thursday evening, she and other commuters were warned that there was a large gathering of young people inside the station.

Some "Facebook thing," they were told.

Oh, no.

A South Street-style "flash mob," she thought.

"I watched the faces of the people getting off the train," said Smith, of Blackwood. "They were shocked."

But what they found was not a riot, but people standing around as if time had stopped.

It was a flash mob, but of the whimsical type.

Amtrak police estimated that about 500 to 600 people participated in the "Frozen 30th Street Station" flash mob, organized by Drexel University students.

People pretending to play musical instruments, toss a football, or read a newspaper froze in place for three minutes starting at 6:30.

One man was on bended knee, fake-proposing marriage to another man while holding out a roll of Charmin Ultrasoft.

"That many kids together usually leads to problems," Smith said.

"But," she conceded, "it was a peaceful thing."

"As long as it all stays positive, it's fine," said Michelle Green, 53, of Southwest Philadelphia, another commuter who also said she was alarmed when she entered the station.

Amtrak spokeswoman Karina Romero said passengers were warned about the event on trains as they arrived at the station, and additional Amtrak police were brought in as a precaution.

"I hear it was quite the sight to see," Romero said.

Of, course, there were the confused commuters with no clue as to what was happening. One muttered "annoying" as he zig-zagged through the maze of temporary statues.

Amtrak reported no commuter interruptions. "Everything went very smoothly," Romero said.

A grinning Jon McGrath, 22, also a Drexel student, took the opportunity to place leaflets for his church in the hands of the helpless flash mobbers.

"It's like a perfect opportunity," he said. "They can't not take it."

Jay Patel, 21, a student at Drexel College of Medicine, joined in the fun, as did some of his friends, one of whom was dressed as Waldo from the children's books and another as Superman.

"Waldo didn't freeze, but Superman did," Patel noted afterward.

When the Amtrak clock hit 6:33, the crowd cheered and applauded.

"Today was a good show of how this city could come together and be peaceful," Patel said.