Today is April 25th, which marks the 38th anniversary of the release of Gradius on the Nintendo Famicom in Japan – which also means that the Konami code hidden within the game turns 38 today, too.
The world's most famous cheat code was added to the game by the late Kazuhisa Hashimoto after he found it was too difficult to play through during testing. Tapping in up, up, down, down, left, right, left, right, B, A and Start gives you a full selection of power-ups, making things a lot easier.
The code was never supposed to make it into the final retail version of the game, but it was – and Konami has subsequently included it in many titles released since then. Even non-Konami games have included the code over the years.
New uses of the Konami code are being discovered all of the time; it was recently found in Castlevania: Legacy of Darkness on the N64, 25 years after the game's release.