Image imported from derpibooru 
Original Description:
 
A mishap occurred that turned (left to right, foals) April, Donnie, Mikey, Raph, Leo, and Casey into foals. Well..Shini and Karai were victims too but they’re offscreen.
 
Delta got left with the foals as her assistant chases Karai and Shini offscreen. And..It’s not only that, but she has to feed the foals as well and the ones not eating right now are impatient and don’t want to wait their turn, hence the reason Leo is telling his brother that.