Atlantis. The Holy Grail. That episode of Star Trek where Captain Picard dresses in drag and does the macarena.
They are things lost forever to the cruel winds of time, and yet they continue to capture the imaginations of successive generations.
Gaming has its own graveyard of historical curios: half-born ideas and ill-fated projects that fell to the red pen of a corporate accountant.
They're called vapourware, and it looks like the Wii is on the cusp of its first two vapourware titles: the elusive Project H.A.M.M.E.R. and the mysterious Sadness.
But as we patiently wait to hear the final fate of those two titles, we decided to cast a tearful eye over past Nintendo games that were coldly struck down before they ever had the chance to fill a gamer's day with sunshine, to place a smile on the face of a child. These, friends, are the games that never were.
NES - Final Fantasy IV
Cheeky Squaresoft. In the flush of success with their initial Final Fantasy games, they cobbled together a screenshot of what they 'imagined' the next game would look like, along with a cunning press release that promised new job classes like "cook" and "carpenter".
That's right - though planned, the game never existed at all, and the company instead opted to dedicate their resources to their first SNES title - the Final Fantasy IV we know and love today.
NES - Drac's Night Out
A woeful tale of in-game advertising run amok. Drac's Night Out got its funding by promising Reebok to put its protagonist, Dracula, into a pair of then-popular pumps.
You'd then guide the vampire to his girlfriend's house for a bloodsucking rendezvous.
But like Dracula himself, Drac's Night Out never saw the light of day, though a prototype of the game sold on eBay for $760 in 2005.
NES - SimCity
A recent discovery, this. Back in 2005, somebody doing the housework at Ninty HQ discovered a SimCity development cartridge - reportedly the only one ever made.
If it really was going to be developed, it makes a kind of cosmic sense, given that the NES was practically the only console that never received a SimCity port.
NES - California Raisins: The Grape Escape
With such corkers as McDonald Land (McDonald's) and Yo! Noid (Domino's Pizza), the NES was no stranger to the awkward advergame.
But this would have been different. Hammered into shape by Capcom, California Raisins' gameplay resembled some of the company's other NES classics such as Duck Tales and Chip 'n Dale Rescue Rangers.
Sadly, the claymation raisins' waning popularity led to the finished game getting axed before release.
NES - Master Fighter II
Okay, this isn't exactly a cancelled game. In fact, it wasn't even legal. Master Fighter II was a pirated Famicom conversion of the SNES's Street Fighter II.
Amazingly, its gameplay remained pretty faithful to its bigger brother despite the fact it was all kinds of ripped-off.
This sort of piracy is common in China, where shoppers can even pick up some crazy soul's conversion of Final Fantasy VII (which originally came on three CDs, remember) for the NES.
SNES - Final Fantasy Extreme
Despite the worldwide success of its Final Fantasy franchise, Square was always worried about how to market it to the West.
Final Fantasy VI was one game to fall prey to such short-sightedness, with translator Ted Woolsey explaining at the time that "it's just not accessible enough to the average gamer".