In the Atari 400/800 port of Donkey Kong, you can view the programmer's initials (LMD) if you do the following:
• Play a game and set a highscore of x37 xxx, x73 xxx or x77 xxx
• Get a game over, with your last death being a long fall
• Set the difficulty to 4 by pressing Option three times
• Wait through the demo screen until the initials appear
This was not discovered until 26 years after the game was released, a year after LMD announced its existence.