Colin Booth had figured it out.
The 8-year-old was sure that the real Santa was not at Springfield Mall, sitting merrily in a green chair opposite the Gap. The real Kris Kringle was at that very moment "flying somewhere over Russia," Colin said.
So who was the very convincing white-bearded fellow in the red velvet suit just a few hundred yards away from Colin and his brother and sisters?
"A helper," Colin said confidently. "But I'm still excited. I didn't even fall asleep yesterday."
In some parts of the mall, shoppers focused on finding the perfect stocking stuffer or pair of earrings. But for many, Christmas Eve was one last opportunity to put their children on Santa's lap.
(The line to see St. Nick had to be cut off at 3 p.m., of course, because Santa had pressing business to address after dark.)
Year after year, the Booths of Wallingford mark their Christmases in photos of the children with the Springfield Mall Santa - the same Santa since Jake, 11, was a baby.
"He takes a lot of time with the kids," said mother Cheryl Booth.
Kiera Booth, 9, was thrilled as she neared the front of the line, but still puzzled by the question of how Santa manages to deliver all those presents in one night.
"I guess he can do it because he travels with his magic reindeer," Kiera said.
"He flies through the sky," agreed younger sister Kaila, 6.
For some, Christmas Eve Santa photos are a tradition. But for others, the holiday just sneaked up on them.
Norine Bastian of Haverford looked around at a line that snaked past the Disney Store to Gap Kids - a 90-minute wait, by the photo elves' estimate - and sighed.
"We thought on Christmas Eve, there would be no line," said Bastian, who stood with children Kolbe, 7; Brynn, 5; and Blaise, 3.
Bastian said she was hopeful this would be the first year that all three of her children would sit with Santa. Blaise was still a question mark, she thought.
When it was the Bastians' turn, Blaise gingerly approached the jolly old elf. His big brother and sister gamely hopped up on Santa's lap, but when Santa offered a little footstool near his feet for Blaise to sit on, Blaise relaxed, an acceptable compromise achieved.
The photo elf shook a red wooden stick with jingle bells. "Smile big!" she shouted. "Woohoo, guys, look here! Cheese!"
The Bastians smiled, and Norine Bastian gave a little shout of relief as she looked at the finished product.
"That was great," she said. "Way to go, guys, high-fives!"
Christmas attire varied widely. Some children were dressed in their finest - stiff taffeta dresses for the girls, sweaters and khakis for the boys. Others were in everyday T-shirts, perhaps a Santa hat thrown on for good measure.
For brothers Troy and Kye Preston, 6 and 4, from West Philadelphia, it was matching royal blue sweaters.
"They hate it," explained their mother, Kristen, "but it looks good in pictures."
Cassidy Komar, 7, of Havertown, wore a fancy white-and-black dress and a big smile. Her brother Tommy, 4, had a red sweater and a worried expression. The balloon animals another elf was handing out to children in line were vexing him.
"I don't want a hat!" Tommy shouted. "I don't want a hat!"
Carter Verlinghieri, 6 months, was dressed as an elf in a red-and-white striped onesie, a green "My First Christmas" bib, and a stocking cap.
Carter's mother, Marianne, of Secane, was a little worried about how her son would take to Santa.
"He's never seen anyone with a beard before," said Verlinghieri, who arrived at the mall at 8 a.m. - a full two hours before Santa began entertaining visitors - to make sure her little guy was in and out quickly.
She didn't have to worry. Santa is an old pro with babies, and Carter went right to him.
There was no chance of D.J. Ravnell refusing to see Santa. The 5-year-old from Collingdale hopped from one foot to another, craning his neck to get the best view of the big guy.
"I'm going to ask for a Michael Jackson dance," D.J. said, inching closer to the red carpet that led to Santa.
His sister Paige, 2, was pretty excited, too.
"Santa!" she shouted when she got a glimpse of him, attempting to break free of mother Lani.
When it was finally their turn, D.J. ran over and hopped up on Santa's lap, a big grin on his face. The little boy ticked things off on his fingers as he explained what he wanted for Christmas, and Santa nodded knowingly, whispering in his ear a little.
After the photo was over, D.J. couldn't resist a question.
"Santa, how does your reindeer fly?" D.J. asked.
Santa let out a belly laugh and his best ho ho ho.
"I can't tell you," said Santa. "It's Christmas magic."