Welcome, fast-foodies, to the all-beef-patty disco. In the new Wendy's commercial, a pounding electro-synth track has got happy little burgers shimmying and jumping, and TV watchers wondering where it came from. ''Satisfaction,'' a two-year-old song from Italian DJ-producer Benny Benassi that topped the dance charts back in 2003, recently reentered the top 10, thanks to the advertisement, and has become iTunes' No. 2 dance single. Though the song's lyrics (''Push me/And then just touch me/Till I can get my satisfaction'') aren't typical lunch-break fare, in context it succeeds even when it comes to Benassi himself. The song's creator tells EW: ''I never used to eat burgers and french fries or drink cola, [but] on my last tour in the USA, I got sudden pangs and stuffed myself full of it. The commercial must be working!''