Revealing mistake: Death's right foot disappears when he gets up after he says "You know, my ankle is starting to feel better." (00:21:15)
Revealing mistake: While Lois is unbuttoning her shirt, Death's feet and legs aren't visible on the couch, even though he is lying on it.
Answer: Mort is Jewish, and Walt Disney was said to be antisemitic. So it would make sense in a Disney universe all the inhabitants would share his supposed beliefs.
MasterOfAll