My Little Pony: Friendship is Magic - Image #232,007

Scootaloo, stop that silliness right now.
Your weight as a full grown pegasus could break Rainbow Dash's neck.

UNLESS pegasi have lighter bone mass, in order to achieve flight. This is worth research

@Ephemeral_Athambia
Indeed!
Not only would that help to differentiate them as a species, but it would also explain why they are the only ones who can walk on clouds! Although that would also make their bones brittle and more susceptible to breakage.