My purchase came with a warning: "Don't open the bag until you get to your car.''That was the edict from the sales clerk at International Plaza's Disney Store when I bought my daughter a princess dress from the hit movie Frozen.Open it inside the mall and I could get mobbed. That's how crazy demand is for the merchandise.Disney knew it had a hit with the royal story of sisters Elsa and Anna in the kingdom of Arendelle, but they had no idea it would be this huge. Since its release in late November, Frozen has become the highest-grossing animated film in history, pulling in $1.2 billion at box offices worldwide.Its success has led to a global shortage of licensed goods, forcing desperate parents to stalk stores and websites for the elusive dolls, plush toys and dresses that in some cases have sold for hundreds of dollars over retail price.Even Houdini would be impressed at how quickly this stuff disappears.• • •For the past three Saturdays, Robert and Arrica Cooper have driven from Spring Hill to Tampa to stand in line to buy Frozen items at the Disney Store, one of three in the Tampa Bay area. They're looking for anything with Elsa and Anna, but they also want items for the movie's other main characters, ice cutter Kristoff, his reindeer friend Sven, and Olaf, a wisecracking, sweet snowman."We'll take anything,'' said Robert, who was shopping for his 4-year-old daughter and four nieces.This month, Disney Stores nationwide took the drastic step of limiting sales of the most popular Frozen products to Saturdays. Stores that get a shipment of dresses have "opportunity drawings'' that customers can enter to buy a $49.95 dress.Disney set up the system to make the process predictable and fair. Basically, they wanted to avoid the Black Friday-like nastiness that had been taking over the stores.Shoppers line up hours before doors open for dibs on whatever magically arrived that week. One Saturday it might be the Barbie doll version of Anna and the stuffed animal of Sven. Another day it might be the plush toy of Elsa and a figurine set. You never know.Last week, the Tampa store scored the mother lode: 122 sparkling Elsa dresses in all sizes. The 55 parents in line, including the first person who arrived at 7 a.m., cheered. Really.Purchasing a dress is a process. You fill out the "opportunity drawing'' for a particular size between 10 and 11:15 a.m. At 11:15, the names are drawn and winners have until the end of the day to make their purchase. You must present your drawing voucher and matching ID. You must be over 16.Buying plutonium seems less complicated.The Coopers purchased one dress each and two of everything else, the maximum allowed. In all, they spent about $600. And they weren't done yet."We're going to be back next week because they didn't have everything we wanted,'' Robert said.• • •Even Disney, the king of marketing, underestimated the power of Frozen, a tale of a fearless princess who sets out to find her estranged sister whose icy powers trapped the kingdom into eternal winter.Stores bought aggressively for the products and, at one point, even airlifted goods from China to distribution centers.Disney did not specify in its latest earnings report exactly how much Frozen merchandise has sold. The company insists there's no conspiracy to create more buzz over the movie, as some frustrated parents have speculated. It's simply an issue of supply not meeting demand.The mighty mouse never leaves money on the table."Frozen is a global phenomenon that has truly exceeded expectations on every level," said Margita Thompson, a spokeswoman for Disney Consumer Products, in a statement. "We are thrilled that audiences formed instant connections with the characters and are working hard to get additional product into stores as soon as possible.''• • •Frozen-mania dates to late 2012 when the major retailers started placing orders for the merchandise. Not wanting a surplus, buyers based orders on how other recent Disney movies had done, such as Brave, Tangled and Princess and the Frog.The products sold well before the movie came out and were still available in December, during the holiday shopping season, said Jim Silver, editor-in-chief of Time to Play Magazine. That changed in the new year, when demand surged and stores couldn't keep products on shelves."They didn't realize they had a phenomenon until January,'' he said.In early March, Frozen became even bigger when it won a 2014 Academy Award for best original song for Idina Menzel's Let it Go. Then the DVD came out, allowing girls and boys everywhere to watch the movie over and over again. Toy analysts hailed the frenzy as comparable to Cabbage Patch Kids in the 1980s and Tickle Me Elmo dolls in the 1990s."When the video came out, that's when all craziness broke loose,'' Silver said.Solving the supply problem isn't as easy as making more products. Toy companies started placing new orders after the holidays, but it takes about two to three months for products to reach retailers from factories overseas, said Anne-Marie Grill, a spokeswoman for JAKKS Pacific, which designs and markets toys, including some of the Frozen dolls and dresses."We are continuously shipping out Frozen products to retailers, but they sell out as quickly as they hit the shelves,'' Grill said.Complicating matters was the calendar. Demand spiked right before the Chinese new year, observed between Jan. 31 to Feb. 6. The holiday shuts down factories and businesses for up to a month, allowing workers living at the plants time to travel home to be with family."It's a very big impact every year for all the importers and exporters,'' said Canan Unal, import operations manager for MTS Logistics based in New York. "It lasts a very long time.''Disney says products will flow into the stores and parks — even Magic Kingdom has been out — throughout the summer and are expected to be back in full stock in July or August.In the meantime, fans can meet Elsa and Anna at Magic Kingdom's Princess Fairytale Hall. Just reserve a FastPass+, because wait times have been up to four or five hours. The next Disney on Ice show will also feature characters and music from Frozen. But it doesn't come to town for another year. Obviously, someone thinks the demand will be just as strong. I hope my daughter's dress still fits.Susan Thurston can be reached at firstname.lastname@example.org or (813) 225-3110.