Smooth, fluid animation, more impressive when you remember all of it had to be handrawn, this was the first episode in the series, and (arguably) best - though I slightly preferred the second installment "the mechanical monsters". Here Superman foils a mad scientist's death ray, a by-the-numbers template, but still decent cartoon, and the 10 minute-or-so running time is perfect for how thin and bare-bones the material is (another reviewer complained it's too short, but I wouldn't have liked it if it was twenty or thirty minutes), made 1000× better if you mute and sync it to Sufjan Stevens' "The Man of Metropolis Steals our Hearts" (legitimately, it's like a perfect music video for it).
Review of Superman: The Mad Scientist
