They were originally conceived as a way for developers to get credit for the games they worked on. But Easter Eggs are now a way for developers to tip their hat to their fans, a way to joke about the past, surprise alternate endings or a way to interact with their audience in diabolical ways that go beyond the game.
Easter Eggs are now a staple of video game design, so to help celebrate the long weekend let's look back on some of the best Easter Eggs ever made.
NBA JAM was, and is, still one of the greatest sports games that have ever been made. You can actually play some of the older versions in bars around Melbourne. For a game that's over two decades old, it holds up remarkably well.
But while the game was already cool, the developers took it a step further by adding the Fresh Prince of Bel-Air — Will Smith in his prime, some would say — as a secret character in NBA JAM: Tournament Edition. There were plenty of other interesting additions though: Bill Clinton, Hillary Clinton and Al Gore were playable characters in the home console releases of the game. There was even going to be a Mortal Kombat-themed court, although Midway killed the idea in the end.
Metal Gear Solid 3
Kojima crams every Metal Gear game with references to the past, in-jokes and all manner of unexpected surprises. But one of the best, by far and away, was one of the ways you could get past the geriatric sniper, The End.
You see, the old man can't live forever. So you could fight the boss as per normal — or you could simply save the game after the boss fight begins and turn the console off. If you don't return to the game for a week — or if you simply move the time on the console forward — The End simply dies of old age when you return. Genius.
There aren't too many Easter Eggs that involve you walking through walls these days. There's even fewer that ask you to shoot the impaled head of one of the main designers.
And playing the voice-over backwards when you first teleport into the level is a cool trick that doesn't get used often enough these days. Seems like something that belongs in Binding of Isaac, really.
The Binding of Isaac: Afterbirth
There are Easter Eggs, and then there's Edmund McMillen. The crumb trail that he sent Binding of Isaac players on for the Afterbirth expansion borders on the legendary for its intricacy, length and sheer creativity.
If you want to hear a summarised version of the tale that ended up with fans digging holes, you can listen to the segment from the Static Podcast above. It's also got a segment from Hayley about Easter Eggs in Dragon Age: Origins and Dragon Age: Inquisition, as an added bonus.
A "crazy journey". That's how one member of the Trials community described the epic saga that is the Trials Evolution riddle.
This is a riddle for a four-year old game that involved finding planks of wood in game. And then translating the cipher code to uncover instructions that locked a hidden song in-game. A song that had to be run through spectral analysis. Which had morse code. And then evolved into a treasure hunt across four countries.
Borderlands: The Pre-Sequel
My personal favourite: Boganella, the talking shotgun from the locally-made Borderlands: The Pre-Sequel.
It's basically a westie stereotype compressed into the body of a pump-action shotgun. Still not as offensive as some of the sideline comments at the under 15's rugby league on a Saturday morning, though.
Imagine being teleported into a level filled with the sound of some bloke going "moo-moo" into a microphone while a bunch of upright cows charge you with spears and axes.
But why does this bovine hell-hole exist at all? Fans speculated that there was a secret level in the original Diablo thanks to the presence of some cows just outside the crypt in Tristram. If you clicked on them enough times, you'd trigger some special unit dialogues beyond the standard moo-moos.
Because of this, some fans believed in the existence of a secret circle of Cow Hell. It didn't. But Blizzard made damn sure to include a cow level in Diablo 2, although sadly it's on a regular field and not actually in Hell itself.
Star Wars: Rebel Assault 2
FMV games from the 1990's are basically made for riffing, so it's only appropriate that LucasArts put a theatre mode in the game reminiscent of the classic Mystery Science Theatre 3000 TV series. It's pretty accessible: simply hit ALT-V during a cut-scene and type "OVRES".
After you beat the first boss in the original Dark Souls, you wander up to the top of the Undead Asylum and you're abducted — ambushed, really — by a gigantic raven who takes you to the Firelink shrine at Lordran.
But there's a cool way to return to the asylum. After unlocking an elevator, travelling to a broken roof, running over some beams and wandering over some mossy rocks, you'll come across a nest. From there, you can squat down and "pretend" to be an egg. Wait long enough and the raven will fly past, pick you up and drop you off at the asylum.
The enemies are tougher but there's two good reasons to jump through the hoops: you'll get the rusted iron ring that eliminates movement penalties in water, swamp or tar-pits, and the peculiar doll which grants access to the Painted World of Ariamis.
Mortal Kombat 1, 2 and 3
The debug menu in the original Mortal Kombat arcade cabinets lay hidden for over two decades before finally being uncovered late last year. Footage of them being broken open surfaced last month, with the menus containing all manner of goodies.
The menus had a range of tools from diagnostic tests, the ability to view every fatality, coin bookkeeping and even the ability to play a Space Invaders/Galaga-esque style game. For a few seconds, at least.
So that's my list of some of the 10 best Easter Eggs in video games. What are your favourites?