Ambulance is an Eddsworld short. It was voiced and animated by Edd Gould.
A man with blonde hair wakes up in a pool of blood pondering what has happened to him, while a man with messy black hair tells him "Don't worry, I called you an ambulance while you were unconscious". The scene then cuts to a clip of the black-haired man literally calling him an ambulance, by pointing and repeatedly shouting "You're an ambulance!".
Watch the video here