102108soup.jpgThe big Pop Burger location that opened on East 58th Street last winter has gotten a threatening letter from lawyers because of a wall-length mural depicting Andy Warhol's famed Campbell's soup cans. What's funny is that it's not the Warhol estate who sent the C&D, but the Campbell corporation, who contend that customers will think that the burger mecca is "affiliated with or sponsored by Campbell in some way." Speaking to the Post, a Pop Burger rep went ape on the 139-year-old soup company: "Who knew that Campbell's Soup still existed? The only reason they are probably still in business is because Andy gave them a place in pop culture history that will forever be celebrated as some of the best art work ever created. And as for their request—come and try to take them down. They don't have a can to p - - - in or a window to throw it out of regarding the legality of their request."