Highlander/WMG

Highlander II the Quickening was just a weird reality that Connor MacLeod made after he got the godlike power that the prize provided him.
It explains quite a bit.

He essentially became a reality-warping deity who then changed the current world into a construct where anything he desired would come true. He wanted a world where he saves everyone by building a sun shield and so it occurred. Then after living in that fantasy for 25 years he got old and senile and then remade reality so that immortals are now from the planet Zeist.

Connor longs for the days of his youth so he makes himself young and immortal again, and then conjures up some villains to fight such as General Katana, a construct of Connor's imagination given form through Connor's use of the Prize's power.

He missed Ramirez so he brought him back as well.

And there you have Highlander 2 explained.
 * It makes a hell of a lot more sense than the film's actual "canon"...
 * Seconded. If only he "imagined" the cast and crew were busy for the other films.

The Prize is based around what the winner wants. It's not an immutable prize. (So Connor gets what he wants, while The Kurgan would be able to live forever and rule ze world.)

 * Or, alternatively, the main part of the Prize (which is the ability to connect with and influence every mind in the world, as Connor explains at the end of the first film) is the same no matter who wins -- Connor would use that power to help the world, while the Kurgan would use that power to rule the world. But in addition to that, the Prize also grants the winner their heart's desire -- for Connor that's mortality and ability to have children; for the Kurgan that'd probably be something to make him even more powerful.

Connor was already immortal during the MacLeod/Frazer battle.
There are two pieces of evidence. The first is that The Kurgan is trying to take Connor's head. All other evidence shows that this would have denied him a Quickening. Second is the fact that Connor felt The Kurgan's presence. He even told Ramirez that he'd felt it once before during that battle. While immortals can detect pre-immortals, the reverse is not true.

Most likely Connor had recently died in some sort of accident while alone. He awoke believing he'd merely been unconscious for a time and was otherwise uninjured. He then went about his life until the day of the battle. It simply hadn't been long enough for him to have aged noticeably or sustain any injuries that would display rapid healing. It's even possible The Kurgan arranged the "accident" a few days before the battle.
 * Or, rather, the first film did not have the "become immortal after first death" rule that later became canon. That is, Connor was always immortal, he just didn't know it until after he survived what should have been fatal wounds. This also goes a long way to explain the Scotland quickening scene with Connor and Ramirez.

The redneck in the first movie was becoming an Immortal.
We see him driving around New York with a trunk full of guns, already odd behavior. He seems drawn to the alleyway where the Kurgan and Kastagir are fighting, and stands and watches with rapt attention, eventually trying to kill the Kurgan. In response, the Kurgan stabs the redneck (much like he had MacLeod) and throws him across the alley... but the man survives, and later tells the police that the doctors say he's healing faster than normal. Clearly, he was to become an Immortal. What effect the Gathering and the claiming of the Prize has on all this, who knows.

The prize can never be well and truly won.
That is to say, that the "Prize" is to be the last immortal left, for now. In The Source, there is mention made of the first generation of immortals, with only two individuals left alive. So, the Prize is to survive long enough to train the first of the new generation of immortals. Could be that the Prize winner ages and dies eventually, or that one of the new generation of immortals takes his/her head, killing off the previous generation. With this, the Game can and will continue ad infinitum.

New immortals come from wasted quickenings.
When an immortal loses his head at mortal hands or by accident, and in the absence of another immortal, the energy doesn't just disappear but instead gets diluted in the world population.

When Connor was banished from Zeist in Highlander 2 he was sent back in time and had his memory wiped.
As the Spoony One explained at length in his review of Highlander 2, the whole "alien from the planet Zeist" thing opens up a metric fuckton of plotholes...unless you assume that when Connor, Ramirez, and all the other Immortals were banished from Zeist they were transported into Earth's distant past and had their memories wiped. Why? Well, obviously so they won't be able to pool their efforts and find a way to travel back to Zeist on their own. They won't have the knowledge to build a ship or a teleporter or whatever, and the technology available is too primitive anyway.

If you think about it this solves a surprising number of plotholes. Why does Katana still look so young when Macleod is now an old man? Why does Katana send his minions to Earth to kill Macleod even though Macleod obviously had no intention of returning to Zeist? Why did Katana bother to go down and try to kill Macleod at all?

Because from Katana's perspective, Macleod only just left Zeist.


 * Sadly, this also provides explanation for many other plot holes. Katana is not the absolute ruler of Zeist, but he wants to be. The Priests held the trial and passed sentence as Katana looked on in frustration. Katana wanted Macleod dead as an act of defiance against the Priests, but could only send his two idiot goons instead of an army because he had to do it in secret or risk the Priests coming down on him. Katana didn't know that Macleod killing his henchmen would make him immortal again because the Priests didn't tell him.

Regarding Highlander - The Source: The Guardian is actually a time-travelling Edward Cullen.
Well, it explains his super-speed.

If The Kurgan would have won, he would have become The God Emperor of mankind
Besides the fact that they are both depicted as very large men with flowing black hair, a variety of similarities are present

1. Ramirez says, about the Kurgan "If he wins the Prize, mortal man would suffer an eternity of darkness.", and humanity in 40k is in a fairly dark age.

2. when Connor wins the prize, he says "I feel everything! I know... I know everything! I am everything!" emplying that winning the prize is to make the winner a very powerful phychic, perhaps even the most powerful pychic of mankind.

3. The God Emperor of Mankind was said to be born in the second millenium B.C., which, given the Future Imperfect history in 40k, is a fairly accurate estimate.

That being said i could easily imagine one such as the Kurgan having many more than 20 sons in his life (though i would estimate that as the amount he would keep alive), though he would see him frightened by the realization that he is no longer immortal, but it turned out alright, because The Emperor is, for all intents and purposes,unable to die.
 * The Primarchs are clones, remember?
 * The iqnuisition would rather not mention that the God-Emperor was a rapist, so of course they cooked up a story to
 * replace it, I mean,has the Imperium of Man ever made test-tube babies before or after the creation of the primarchs?

Winning the Game equates to becoming the Emperor of Warhammer 40k
The Emperor is canonically a sort of composite soul of Mankind's shamans. Presumably the canon version, a ritual in which they sacrificed themselves to form Emperor, is a metaphor or a misunderstanding of what really happened: they gave their lives to reincarnate as Immortals. They then duelled each other until there was the Only One.

At least one wandering immortal in Judeo-Christian folklore was really Methos
He seems to be as old as Western civilization, and according to The Other Wiki he has spent time in the Middle East, so he'd have had plenty of opportunity to inspire the legends of Cain or the Wandering Jew.

The Watchers are a division of the Watcher's Council from Buffy
Over time, the Watchers realized that not all immortals were vampires or demons, they were just ordinary humans. So the Council divided into two sections, one that remained devoted to the slayers, and one that studied immortals.
 * And The Immortal in "The Girl In Question" was one of the HL guys.