I was stopped in front of my friends house and I forgot that I was in reverse. So when I put the emergency brake on and let out the clutch I stalled.

I know I shouldn't have done it, but does this cause any damage?

 

Unless you do it day after day after day it's fine. Toyota wouldn't build an engine or transmission that gave out over a simple stall every once and a while

 

Maybe the same as stalling in first?

 

it happens, don't stress yourself.