It being too late to order anything online, thousands of people showed up in downtown San Francisco on Saturday to do the Christmas shopping thing the other way, with bags.

There were bags under arms, over shoulders, in backpacks and in carts. The people holding the bags were moving fast, the way people holding bags often do. Union Square could have passed for the airport, except for the lack of planes.

In some cases, the people carrying bags also carried children.

“We’re looking for things that tickle our fancy,” said Gabriel Thomas of San Jose, who was hauling his 5-year-old daughter, Ruby, on his shoulders while his wife, Freida, carried their 2-year-old daughter on hers. It was at least as cute as anything in the kitten adoption window at Macy’s.

From her perch on high, Ruby said she sure could have used a set of toy trains that she saw in a department store. Down below, Gabriel said he was too busy carrying Ruby to carry a railroad, even a small one.

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Upside-down Christmas tree at S.F.'s Westfield mall, video taken on Nov. 27, 2017

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A lot of shoppers already knew what they were getting for Christmas. Among these was Sweetpea the Chihuahua, who was walking down O’Farrell Street in a red cashmere sweater that her owner, Graham Myers of San Francisco, bought for her weeks ago.

“I gave her the sweater early, because it’s been so cold,” Myers said. “I didn’t want her to have to wait until Christmas.”

Sweetpea appeared grateful. Myers said that his dog can tell the difference between cashmere and lesser materials and that Christmas is not the time to cheap out on your only housemate.

He did manage to pick up for himself, with Sweetpea’s approval, a pair of brown pants that were on sale. He carried them and a pair of new shoes in one hand, and he carried Sweetpea’s leash in the other. That meant, he said, that he was plumb out of hands for carrying any more stuff.

At the Union Square ice skating rink, a long line of Brian Boitano wannabes had formed at the box office for the opening skating session. The smart thing to do, said one skater, is to skate first and shop second. That way your arms are free of packages and you can catch yourself before your rear end hits the ice.

Maureen Gradek of Healdsburg, who came to the rink with three kids and four grandkids, said she was all done skating and shopping for 2017. Her son Colin would be getting a carburetor for Christmas.

Colin, who wasn’t skating either, said he already knew he was getting a carburetor for Christmas because he had to tell his mom last month which carburetor to get. It’s a carburetor for a 1964 Chevy pickup, a part even harder to find than a 1964 Chevy pickup, and it’s wrapped up under the tree at home, in red and white striped paper.

“I think it’s really exciting,” he said. “It’s what I always wanted for Christmas. Now I can get my truck to run again. It hasn’t run for a year.”

Gradek said Colin had been a good boy this year and deserved his carburetor. Besides, he waited patiently while she went into Macy’s to shop for things besides carburetors, which are about the only things Macy’s doesn’t carry.

Macy’s does carry puppies and kittens, or at least it allows the San Francisco SPCA to display them in its storefront windows. A small crowd had gathered to watch a gray kitten audition for a possible adoption by swatting a ball around its enclosure, very cutely. Meanwhile, SPCA volunteers collected donations and urged softies to step inside and sign up for a kitten or a puppy. A sign said 182 people already had.

The shopping area around Union Square was full of sales, most of them with the phrase “up to” in them. At the Gap, stuff was up to 60 percent off. At H&M, stuff was up to 70 percent off, and at Old Navy stuff was up to 75 percent off.

The “up to” stuff was by the front door. The 75-percent-off stuff wasn’t.

Kim Resso and her 13-year-old daughter, Jillian, had come from Modesto for last-minute shopping and a night on the town. Jillian picked out a pair of boots for Christmas, and Kim said it was OK for her to wear them that evening, when the two of them were going to see “A Christmas Carol.” After that, the boots would go back in the box and be whisked back to Modesto to go under the tree, where Jillian would try her best to be surprised on Monday morning.

“This is a better way,” Mom said. “I usually shop online, but with her, it’s too risky. I don’t want to drive back and forth from Modesto again to exchange boots.”

Most people knew it was Christmas because of the nonstop carols coming out of loudspeakers, because of the bright red T-shirts on the tattooed techies in the Apple store, because of the tinkle of Salvation Army bells and because the never-ending subway construction morass on Stockton Street was plastered over once again by the seasonal cover of fake grass.

The subway to Chinatown may be running way behind, but Christmas is still scheduled for Monday, exactly one day before the stores reopen for exchanges and refunds.

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com