Game designers love to hide things in their virtual worlds. An in-joke, a weird object, a strange play mode – whatever it is, they're usually all discovered within weeks of release. But YouTube gamer Lord Zedd has just found a secret feature in Halo 3 seven years after the launch of the classic sci-fi shooter.

It turns out that if you load the game up on Christmas day (or change your Xbox 360 clock to make your machine think it's Christmas day), then press both Xbox thumbsticks down, the loading screen shows a new view of the eponymous Halo space ring, complete with a scrolling message reading, "Happy Birthday Lauren". The text, it seems, was included by one member of the development team, Adrian Perez, who directed it to his wife and never expected it to be found.

Bungie, the studio behind the Halo titles, had hinted to fans on at least two occasions that a final hidden treat – or "easter egg" in gaming parlance – remained stashed away in the game after many others were found. Now finally, the seasonal treat is available to all – and 170,000 have already watched the video.

Implanting hidden features, items and messages in games has been around since the very beginning of the industry. Warren Robinett, designer of 1979 title Adventure claims the term was coined by an executive at Atari where the practice was actively encouraged. Memorable examples have included Indiana Jones's remains showing up in Fallout: New Vegas and the bit in Metal Gear Solid 3 where a character dies of old age if you leave the game running for a week.

Although impressively well hidden, the Halo 3 example falls far short of gaming's most elusive easter egg. That honor surely goes to programmer Landon Dyer who hid his own initials so deeply within his home computer conversion of arcade hit Donkey Kong that it took another programmer 26 years to find them.

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