Our high school had a DEC PDP-11, and I remember my brother trying to write a version of Pac-Man using only the ASCII characters available. There was one test run where the monsters started eating the maze, and it was back to the drawing board. While my brother was working, he was constantly pestered by a classmate who wanted to "help," but was way out of his league. Since my brother showed an aptitude for programming, he was made an assistant admin, which gave him special access. When he finally finished the game—and it worked beautifully—the pest was insistent that he was going to write a Pac-Man game, too.
That's when my brother told him, "Oh, don't knock yourself out. I finally figured out the secret." Behind the scenes, my brother had already created a system command that linked "pacman" to his lengthy game code. So right in front of the pest he typed:
And the game started running right there! The pest freaked and ran for a terminal to try it himself. Meanwhile my brother was furiously removing the command link. So when the pest couldn't get the same three lines to work, my brother just innocently asked him, "Are you sure you typed it correctly?"