Forget the iPod, Wii game console or giant plasma television.

This year's must-have holiday item was an 8.3-ounce can of Red Bull.

The high-octane, caffeinated energy drink apparently helped weary retail workers get through the marathon shopping hours offered by many stores in the final days before Christmas.

"We've been downing Red Bull," said a GameStop employee at the King of Prussia Mall who started work at 8 a.m. yesterday after working until midnight Saturday.

Chris Stackhouse, a manager at the Haagen-Dazs store across from GameStop, said he began to stock Red Bull a few days ago after noticing an increasing number of mall employees slurping the sugary drink on their breaks. Over the weekend, he sold roughly 100 cans a day, he said.

While stores in the New York area pulled unprecedented all-nighters, many retailers in this region opted for midnight closings as merchants struggled to keep up with Internet shopping sales and to reverse a trend toward less consumer spending.

The late-night hours, however, took a toll on workers and perhaps productivity, too.

"I'm so tired," said King of Prussia Toys "R" Us employee Shekyda Lawhorn, who worked until 12:30 a.m. Sunday, then came back at 8 a.m. "I'm not falling asleep at the register but I'm messing up a lot. I keep forgetting to push the gift-receipt button."

Late yesterday, the roads leading to the King of Prussia Mall were jammed as brake lights blinked on and off like a Christmas light show.

Like most area malls, King of Prussia boasted "extended holiday hours" from 8 a.m. to 11 p.m., while anchor stores like Macy's and Sears opened at 7 a.m. and closed at midnight from mid-December through yesterday. And most malls and stores will be open until 6 p.m. today as retailers seek to capitalize on procrastinators.

Stuart Appelbaum, president of the Retail, Wholesale and Department Store Union, said extended hours hurt workers nationwide.

"Retail workers have a lot of stress at this time, not just about time taken away from families, but also worries about how to meet their families' needs," Appelbaum said.

After working 7 a.m. to 3 p.m. yesterday, JCPenney employee Sirren Bright said she wasn't relishing the thought of going home and peeling sweet potatoes for the Christmas Day dinner she planned to host in her Norristown home.

Bright and Michael Brown, her colleague in the shoe department at the King of Prussia store, were so cranky they started to bicker over who was more tired.

"I've been here since 7 a.m.," Bright said.

"Well, I was here until 11:45 p.m. last night," Brown snorted.

"Excuse me - the other day I worked till about 10 or 11 p.m. and then I came in the next day around 8 a.m.," Bright retorted.

"He's a grouch," she added.

"I'm the Grinch," he snapped. "Get it right."

During the morning staff meeting yesterday, workers reported that JCPenney managers handed out a flier that said something like, "Please try to be nice to customers. Only two more days to go."

Yesterday, Regina Smith, a masseuse at Vital Touch Massage, said she was giving a 20-percent discount to King of Prussia employees.

"Mall employees mostly want you to focus on their upper body," Smith said. "That's where everyone holds all their tension - in the neck and shoulders."

Too bad Vital Touch didn't offer foot massages.

"My feet kill," said Megan Careless, a 21-year-old employee at J Crew. "It's like an ongoing pain."

Mall kiosk worker Hagay Mazal Tov and his partner David Dayan said they were surviving the long hours by doing what so many other mall employees were doing - running on those Bulls.

"This weekend we drank a whole case of Red Bull - 12 each," said Dayan, who was selling iPod and cell-phone accessories at a small stand called Street Talk.

As for Stackhouse of Haagen- Dazs, he said he doesn't touch the stuff. He drank so much of it on Black Friday last year that he started shaking and sweating. Then he passed out on the mall floor and paramedics took him away in an ambulance, he said.

"I had a caffeine attack," he said. "Now I only drink natural stuff, like coffee."

The Associated Press contributed to this report.