The phrase "go ahead, make my day" was written by Charles B. Pierce, an independent filmmaker who is credited with "story by" in the film Sudden Impact. 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".

In 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. However, the surviving robber grabs the fleeing waitress Loretta (Mara Corday), holds his gun to her head, and threatens to shoot. Instead of backing off, Harry points his .44 Magnum revolver into the man's face and dares him to shoot, saying with clenched teeth and in his characteristic rough grumble, "Go ahead, make my day," meaning that if the robber attempts to harm Loretta in any way, Harry would be happy to dispatch the robber.

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