Twenty-one seasons in, The Simpsons continues to shine as a beacon of smart, funny TV. But it is also one of our favorite cultural fun-house mirrors, and we'd be remiss if we didn't spend a moment looking back on the decade of pop that was through the prism that is America's best dysfunctional animated family. As we usher in 2010, we share our Top 10 picks for the best pop star appearances on The Simpsons over the last ten years (with "pop" being v-e-r-y loosely defined in order to accommodate our faves). Our list is in chronological order, making it all the easier to see how music—and the show—evolved through the 00s (starting with bubblegum pop, ending with edgier acts). Is anyone surprised that Bart, Homer, Marge Lisa and the gang have had longer careers than some of their guests? More »