 The actual origins of the phrase came from Pierce's father Mack, who used to tell him as a child, "Just let me come home one more day, without you mowing that lawn, son just go ahead... make my day".At the beginning of the movie, Harry Callahan (Clint Eastwood) goes into a diner for a morning cup of coffee where he discovers a robbery in progress.He kills all but one of the robbers in a shootout.