"I've got an electric screwdriver, a hammer, and WD-40 - what else could a girl want?" said Betsey King, who was born and raised in Newtown.
It was a party atmosphere, with friends and neighbors greeting one another and longtime customers chatting with Callahan and his staff.
"I came to this hardware store when I was a little kid," Nancy Romanchek told the owner before leaving with sprinklers, gardening gloves, and a lightbulb. "My dad used to bring me here."
The store has been a fixture under various owners in the close-knit, picturesque borough since 1869, when it started selling carriage bolts and farm equipment.
"Give me an N, give me an E, give me a W!" shouted John Rasiej of Wrightstown, as he led the crowd in chants spelling "Newtown Hardware."
"It's a big event. We want to live it up and create some magic," said Rasiej, who directs plays with the Newtown Arts Company.
Organizing the cash mob to give Callahan and his store a financial boost was local publicist Andy Smith's idea.
"I've seen them popping up around the country for the past year or so," Smith said. "I knew [the store's staff] were holding a campaign to increase business. So I figured it will take 10 minutes for a Facebook thing, and we'll see what happens."
The Facebook message said, "Each 'mobber' is encouraged to spend about $20, although you can spend more if you wish. With spring here, there has to be $20 of stuff you need for around the house - grass seed, a tool, paint, etc."
Word of the gathering also spread on Twitter.
"I got an e-mail from a friend, and it was forwarded to a gajillion people," Romanchek said.
She also spread the word at the Starbucks down the street as she waited for the appointed time.
It was supposed to be a surprise, but Callahan said he "knew something was up this morning, because people were acting funny. They were asking, 'Is everything OK?'
"It wasn't my birthday, it wasn't a surprise party, but it certainly was a surprise," he said.
Starting last spring, Callahan, who said he is "older than 65," gave away 2,000 "Save Newtown Hardware" bumper stickers to boost business, which has been suffering from the weak economy for four years. The red-white-and-blue stickers produced a "bump for about two months, but then it died out," he said.
"Believe me, I can use this," Callahan said as the cash registers rang up the sales.
An hour after the cash mob arrived, the store was nearly back to normal for a Saturday, when it usually grosses $2,000. Callahan estimated the store took in $1,000 in that hour, and it totaled $3,700 in what he called "a really nice day."
"Keep the faith," an old friend, Duane Buck, told Newtown's George Bailey.
Contact staff writer Bill Reed
at 215-801-2964, firstname.lastname@example.org,
or follow @breedbucks on Twitter. Read his blog, "BucksInq," at www.philly.com/bucksinq.