Doom II · PC (MS-DOS) · 1994
The final boss of Doom II, the Icon of Sin, hides the digitised, impaled head of id Software co-founder John Romero behind its wall — and the only way to win is to shoot it.
Doom II's final boss, the Icon of Sin (MAP30), appears as a giant demonic wall that endlessly spawns monsters. The actual target the player must hit is sealed inside its head, invisible during normal play. John Carmack coded the boss so that the kill object was a texture of John Romero's own face, scanned from a photograph and mounted on a spike — using the idclip/noclip cheat to pass through the wall reveals the violently severed head. Romero also recorded a deep, distorted voice clip for the boss that, when played in reverse, says "To win the game, you must kill me, John Romero." The reversed-message gag deliberately echoed the backmasking moral panics once aimed at rock bands, and the whole thing was an in-joke planted by the id team. (The often-repeated "Quake" version of this story is a misattribution: Quake's final boss is Shub-Niggurath, and contains no Romero head.)
On MAP30 ("Icon of Sin"), the head is normally hidden behind the boss wall. Use the idclip (noclip) cheat to walk through the front of the demon's face and you will see Romero's impaled head on a spike — the object that must be struck with rockets to win. Playing the boss's voice clip in reverse reveals the spoken message.