[identity profile] vaf77.livejournal.com 2012-12-04 08:42 pm (UTC)(link)
During the show's opening credits, Maggie is run through a supermarket checkout scanner, which reads that she is worth $847.63 (a reference to the monthly cost of infant-rearing in 1989). In "The Simpsons 138th Episode Spectacular," the scanner instead reads "NRA4EVER," a reference to the running joke that the show's creators are right-wing radicals. In the newer episodes her price has changed to $486.52 (Possibly because of the change in the cost of infant-rearing).

http://simpsons.wikia.com/wiki/Maggie_Simpson