Just when I think I've finally found everything, I stumble across another minor graphical inconsistency: if Penguin Cop dies without a hat (or with only minor headgear), his head bulges upward by a pixel while his hatted forms do not, with the bulge only being corrected after he shuts his eyes. It's most noticeable dying with one of the arm-cannon powers since the cannon also gets slightly distorted along with the head bulge on that frame:
