flying sheep
A large sheep that is commander of all sheep. They are rarely seen, last sighting was in Warcraft 3 and Warcraft 3: Frozen Throne.
That sheep is a flying sheep!
when sheep fly
when your idea is so dumb and unrealistic that it's ugly to look at
Peter: I will be a robot one day and fly to the center of the earth!
Ronald: Yeah sure.... when sheep fly.
Ronald: Yeah sure.... when sheep fly.