What is the sound of Walt Disney Feature Animation imploding? Sadly, it’s the small plaintive whimper made by Dream On Silly Dreamer, an amateur documentary created by shell-shocked Disney artists who got axed when the studio began phasing out traditional, hand-drawn 2-D animation a few years back. (Goodbye, Lion King; hello, Chicken Little.) The DVD edition, with many scenes extended from the original cut, plays like a real-life version of The Office, as artists vent their anger at former Disney managers (including deposed chief Michael Eisner) and mourn the death of a seven-decade-or-so legacy. It’s a unique, nervy home movie, and a heartbreaker.