Because it hails from the Sesame Street region of the Muppet empire, this gaily busy kid flick unspools with a serious lesson in mind: Share your stuff! But for a morality tale aimed at 4-year-olds, it's also charming enough not to bore the relaxed-fit jeans off accompanying adults, especially when Elmo, in pursuit of his beloved blanket, dives into Oscar's fetid garbage can and winds up in a fabulously nasty neighborhood where cranky moviegoers pay bad money to see Sharon Groan star in Basically, It Stinks. And where Mandy Patinkin runs riot (and even sings, dementedly Sondheimishly) as Huxley, Grouchland's greedy villain, while nearby, Vanessa Williams warbles as the Queen of Trash. Every so often, Bert and Ernie stop the action to reassure any tremulous tots that The Adventures of Elmo in Grouchland is only a movie. Where were these guys when we needed them in Eyes Wide Shut?