"The Land Before Time," with Steven Spielberg and George Lucas among its executive producers, is by turns heart-rending and hilarious. A ragtag group of little dinosaurs, separated from their families after an earthquake, seeks the legendary Great Valley in a time of catastrophic drought. The characters are adorable and gracefully animated, each with endearing idiosyncrasies, and the challenges they face teach unobtrusive lessons. Peppy pterodactyl Petrie, for example, is afraid of flying; Littlefoot the Longneck adopts a leadership role, but he's filled with self-doubt and struggles to maintain harmony within the group. The animation is dynamic and imaginative, evoking an unfamiliar, younger Earth as the band roves through prehistoric flora, tar pits and barren wastelands. Although it spawned many sequels, this one has withstood the test of time.