Not only can bumblebees not fly but kangaroos cannot jump. Same mathematical logic. Both of these concepts are based on inaccurate information and assumptions - the bee is a solid mass and not almost completely hollow, the kangaroo weighs and acts the same as a sack of potatoes when various adaptations to muscle make jumping a more efficient method of travel.

I'll dig out some more but I think it may need to be a seperate thread...