The Simpsons reaches an incredible milestone this weekend as it airs its 400th episode, a high profile event that's getting major news coverage and other attention including an animated David Letterman Top 10 list on Thursday night's show.  The show is in its 18th year, the longest running comedy in television history, and is only two years from breaking Gunsmoke's record as the longest running scripted series ever.  It's still drawing great ratings in the States and is a force of nature in foreign markets as well, where it airs in 75 countries. 

The Simpsons has accounted for over $5 billion in licensing for News Corp., and represents 50% or more of Fox's licensing and merchandising, according to Variety. 

One channel for that merchandise has been pop culture stores, which can sell the comics and graphic novels, toys, and special products such as the Homer Simpson talking beer can opener. 

This summer, the Simpsons profile will be raised even higher by the release of the first Simpsons feature film in July (see 'Best in Shows 2007, Part 2').