Amazing this hasn't been brought up yet.
The Shinigami are Time Lords
Specifically, they're a bunch of renegade Time Lords having used up their regenerations. They've been experimenting with genetic engineering for this. The Death Note has both TARDIS and Chameleon Arch technology in it, allowing them to feed. Part of their reason for this is that, like the Weeping Angels, they feed on your potential lifespan-only they just straight up kill you. Ryuk is a clone of the Master.
They "gain" lifespan in a similar way as the Angels do (the Angels transport you to a different timeline and feed off the potential energy. The Shinigami kill people and gain more lifespan). Their powers are only limited to humans, so the Time Lords don't care (who cares about the cosmic equivalent of cavemen?)
- The Doctor!
- One of the reasons the Doctor doesn't reveal his name is the prevent a Death Note from working on him. Yeah, it targets humans, but it's possible that the Shinigami may consider him close enough.
- Maybe not cousins, but an example of divergent evolution. They're the same basic life-form as Weeping Angels(effectively supernatural entities based off mythology), and developed a similar method of eating to their Lonely Assassin relatives.
The death note is a Tardis.
It's bigger on the inside (it has an infinite amount of pages) and it can manipulate events in time and space but it's malfunctioning so that it always brings about the death of those that go inside it.
Aiber is A from Wammy's House
A is a Time Lord who committed suicide to escape Wammy House. However, he still wished to beat L and tried to do so by both exceeding his detective skills (while using the name Eraldo Coil) and by being a con-man that L wouldn't be able to catch. Unfortunately, he failed on both fronts thus losing the right to use the alias "Eraldo Coil" and being forced to either help L when needed or spend a great deal of time in prison. Hence why Aiber uses an "A" to identify himself and is able to act as Eraldo Coil during the Yotsuba arc without anyone noticing any discrepancies between his behavior and Eraldo Coil's known behaviors.
L is a Time Lord
He regenerates into Near. Now, one might ask why Near would have to deduce certain things all over again when he already came to that conclusion as L. The answer is that, like the eighth Doctor, Near is suffering from partial amnesia.
- In addition to the above...
The time lord that is L/Near is a regeneration of Mytho from Princess Tutu
Near, who resembles Mytho is already a regeneration L and Aeon. L and Near have cut out parts of their heart in order to defeat Kira. Notice that neither are ever scared or lonely or loving or anything that might get in the way of their duties. In fact, all they might have is Curiosity. After that, Near reconstructs most of or all of his heart and becomes Aeon.
L is a Time Lord and Naomi Misora was once L's Companion.
They had many adventures of horror and wonder together but she eventually returned to get married to Raye.
Light is also a Time Lord Because a watch is an essential part of the memory restoration process.
...Ergo Light is the Master.
For so long he lived in boredom and despair. There was so much that was rotten but there was nothing he could do. But then one day he realizeed the rules, time, this world
-they are his
to manipulate! Being the only one of his kind (super genius) around didn't make him some freak, it made him VICTORIOUS!
Light is a Time Lord and Ryuk is his Companion.
Who says Companions always have to come from Earth?
Who in turn regenerated into Paul Atreides
However he doesn't remember everything from his past regeneration. It'll explain all of the Gambit Pileups
that were made in the first half. Also, this will explain, why L wasn't really satisfied with his results. And why he still suspected Light, even if he couldn't be the murderer, and why he predicted Light's every move (remember those "fights", that they had?) Think about it.
- The fact he's missing his memory could be from him using the chameleon circuit to avoid the 'Time Lords can recognize each other despite regenerations.'
Mello is a Time Lord.
I think Mello is the child of River Song and the Doctor
- This would explain the gun thing and why when a god of death shows up, everyone else tries to kill it, but Mello? He just calmly hands it a bar of chocolate. That is so Doctor.
- This also explains why he showed Takada his face- he knew the Death Note wouldn't work on him!
- Plus, he physically looks like both River and the eleventh Doctor, as well as Amy and Rory
- He could have regenerated into Willy Wonka.
Mikami is a Cyberman.
It's so OBVIOUS! DELETE! DELETE! DELETE!
L is The Master
In the episode where he dies
L mentions that he can hear bells. While everyone assumed that this was something to do with his human past due to the opening flashback with Big Ben, that isn't necessarily true, and if it is, may actually be part of the fabricated memories implanted when he chameleon arched. When The Doctor psychically connects with The Master in EOT, The Drums...don't really sound like drums. If they were quieter, they could easily be mistaken for bells, and they might well be slightly dulled by the chameleon arch. While this may lead some fans to think that, due to Chameleon Arch personality flips, this makes Light The Doctor, it is my opinion that Aiber is actually The Doctor. What's the one piece of character development we got about him? He hates guns.
It's entirely possible that, (Although not true every time due to 10 training his students in rifles and machine guns as John Smith) that the flip's severity varies, and that when they chameleon arched for whatever reason, The Doctor got a very mild one which put him on the wrong side of the law but left him a mostly peaceful man who despised killing, thus his willingness to work the Kira case, while The Master got a somewhat more severe flip which, while it still left him a somewhat cold manipulator, brought him much closer to good.