Cardcaptor Sakura/WMG

Tomoyo is an Author Avatar
Aside from acting like an older woman and not being one of Sakura's Those Two Guys, Tomoyo happens to have unlimited resources, tapes and designs Sakura's costumes, and manages to always tag along despite the complete inappropriateness of an unpowered muggle doing so. She fawns over how adorable Sakura is, yet cheers her on as pursues Li. These are all things a writer metaphorically does. Thus, Shipping Tomoyo with anyone is authorically incestuous.
 * Another example of hidden avatars is in The Movie, where Li happens to have four much older and surprisingly gushy sisters. This seems unusual, given that the Li family's serious reputation is suggested as the reason for Syaoran's initial coldness, until you realize they probably represent CLAMP.
 * Tomoyo might be as well a supreme magical identity so powerful that can hide her own magic, which would explain it better. Remember Kaho's catchphrase.
 * *Cough* Ichihara Yuuko *cough*
 * One flaw- Real "Syaoran", who can presumably also be referred to as Original Watanuki, has interacted with her at least once, and is rather cold to her, to say the least. If Yuko was Tomoyo, he'd have been much more friendly, treating her as an aunt rather than a potential threat. Also, she would have known his real name, and he would have known that, and as such he would never have used his father's name as an alias in the first place.
 * Negative one flaw- Laser-Guided Amnesia. In Canon.
 * In any case she made the doll of Sakura with costume Sakura wears for Final Judgement. Was it precognition that Sakura would one day wear that outfit? She designed costume for Sakura cause of costume for doll?. Did she beforehand, back when made the doll, want Sakura to wear costume? Was it a coincidence the costumes look identical? There is no such thing as coincidence.
 * Hitsuzen did it.
 * In addition, the AU versions of Tomoyo in Tsubasa both had prophetic dreams, and the one in Japan had other powers as well. Given that each Tsubasa version of a character is supposed to be the same basic person as any other version of the character, it's not a stretch to imagine that CCS Tomoyo also has magical powers.

Kaho is the reincarnation of Yuuko.
It was at hinted above, in a cough, but derserves to be flatly stated. Yes Kaho has alot of magic of her own. That much we all are aware of. To put it bluntly Kaho has said:  That is the big vital clue. Except for the hair colour they look identical! Besides if Eriol is the reincarnation of Clow Reed, then it makes sense Kaho might be reincarnation of Yuuko. With the Timey-Wimey Ball that is Tsubasa Reservoir Chronicle I see no reason why not.
 * In addition, what with CLAMP enforcing their big-time never-split-up-any-official-couple pairings, it seems doubtful that Clow's soul, reincarnation or otherwise would fall for anyone who was not essentially Yuuko.
 * And to further extend this theory, it is possible that Nadeshiko is a reincarnation of Yuuko's as well, regarding her mysteriously early death and the fact that Fujitaka is also a reincarnation of Clow.
 * There is a problem, and that is the line when Kaho saids "There are no coincidences only inevitabilities" is not in the manga. In fact in the manga, Kero and Tomoyo wonder if this was done one purpose but, Kaho saids that it is nothing but a coincidence.

Mei-ling was told by the Li family to pretend she made up being Syaoran's fiancee to ensure Syaoran and Sakura end up together.
The Li family wants the Clow Cards, and it was becoming apparent that not only was Syaoran losing to Sakura, but the deck (so to speak) is also stacked in her favor. But... if Syaoran were to marry Sakura, then their children would likely inherit the Cards as well as be of the Li stock. And Sakura is less likely to rebel against the Li Family the way Clow did.
 * Wasn't it implied in the canon as well?
 * Of course not. That would imply that there might be something complicating Sakura and Syaoran's relationship. (And that the arrangements of their relationship would have to be explained in any shape, way, or form) The anime merely has Mei-Ling "revealing" that the whole fiance thing was something she made up as a child, so it wasn't binding and would dissolve as soon as Syaoran chose someone. ....which makes it exceptionally odd that the Li Family let her chase her pretend fiance to another country. But then, there's nothing about how the Li Family operates either. When Syaoran was first introduced, Kero mentions that the Li family was kinda sinister and a major power in Hong Kong...but all we ever really see of them are Syaoran's sisters who think Sakura and Tomoyo are cute.

Likewise, the Li Family sent Syaoran back to Japan a few years after the series specifically so he could romance Sakura.
Again, resulting in their children being in the Li Family and having the Cards. This is why they're giving him financial backing; an exchange student pass; etc. Syaoran is a good guy and he doesn't want to creep Sakura out with this (hence all he tells her was that "arrangements were made"); and he will treat her well.

Sakura is an ancient ancestor of Milfeulle and Apricot from Galaxy Angel.

 * Well, she and Rico do look a lot alike...
 * Which may explain why she resembles nothing like her mother or father.
 * Does that make Tomoyo an ancestor of the Blancmanche Corporation?

Keroberos and Yue and Spinnel Sun and Ruby Moon were lovers/mates prior to the former's sealing inside the Book of Clow, which wiped their memories of the latter.
Spinnel and Ruby were stated as being "counterparts" to Kero and Yue, and indeed, they both look very similar in both their forms to each other. Also, Spinnel and Ruby needed to hide their true forms from even Yue and Kero until the final test by Eriol, hinting that Kero and Yue had known them prior to then. Then there's the fact that, despite not recognizing him, Kero made fast friends with Spinnel, not really seeming to care that there was a blackish butterfly-winged version of him out there. Clearly they were meant to be an item, and like everything else about Clow Reed, Kero's and Yue's memories of their "partners" were wiped after their sealing. Clow Reed also wanted Yue to fall in love with Sakura via Yukito. He really sucked at playing matchmaker.
 * Er, Word of God says that Ruby Moon and Spinel Sun weren't created until Eriol was reincarnated. So it's not possible for all four Guardians to have known each other before Yue and Kero were sealed. Ruby and Spinel had to hide because Yue and Kero would have sensed their magic.
 * Alternately, Past!Spinel and Past!Ruby were lovers of future!Kero and future!Yue.
 * Could be that Clow was just playing match maker again. Once he saw that the Sakura x Yukito pairing was going down the drain, he decided to at least make appropriate partners for Kero and Yue, considering with those two, they don't have much other choices for relationships, so he possibly can't screw this up again, right? So Spinnel and Kero get off well; success there. Unfortunately, Yue is still Yue, so no hope of a relationship with Ruby. Well Clow, you at least you didn't screw up on everything, there's still one couple that worked out. Plus, there's still thousands of fangirls...ahem I mean suitors for Yue at least..........*cracks up laughing* Okay, okay! Seriously, there's no chance of that. Yue would just reject any fangirl before they have the chance to ask. Clow, just give up while you're behind.
 * Something that may indicate support to this idea is that, while Yue and Kero seem to have a motif that matches Clow's (rather solar [yes, even Yue], more masculine, and light-colored), Ruby and Suppi's designs are inexplicably dark, feminine, and lunar. With the advent of xxxHolic, it doesn't seem too off the bat to think Yuuko was a bit of inspiration for them, intending to match the two pairs together. Of course, Yue/Yukito still decides to screw fate and fall for Touya, but that may have been the original intention.

The reason Clow tied the Cards to Sakura's soul was in order to create a sympathetic resonance within the soul of the Sakura of Tsubasa Reservoir Chronicle, thus creating the Wings.
Ultimately, CCS Sakura isn't going to do anything with her Cards, and they'll probably die when she does; it's highly unlikely she'll do to a successor what Clow did to her. However, the stakes are much, much higher on the multi-dimensional field. The individual Feathers alone are shown to be far more powerful than the Cards.
 * It's been stated that without a power source (that is, their confirmed master), the Clow Cards will eventually fade away and die. Sakura has professed her dear friendship with the Cards, and the Cards with her. As such, it's likely she might not want to do to a possible successor what Clow did to her (but, considering the vastly increased lifespan of powerful magic users, that may easily change eventually); all the same, there is no way in hell Sakura as she is now would allow the Clow Cards, her horde of life-long friends, to just die, and she would feel it far more important to preserve their lives than to avoid putting one person through a hard time just because the same was done to her - especially considering how greatly she ultimately benefited from those troubles.
 * Besides, no one says she has to do to her successor what Clow did to her. It's Sakura; she could conceivably find another way to pass the cards on. Remember, Sakura was the first person to whom the cards had ever been passed on; it's not like there were ten other Cardcaptors before her to set a precedent. And remember, Kero fell asleep. If he hadn't been asleep and had stopped Sakura from opening the book and had taught her about the cards first... things could have been a lot different.
 * Remember also that by the end of the series, Sakura is stated to have become more powerful than Clow Reed himself, and given that she was only ten at the time, her powers could have increased even further. It's possible that she's found a way (or will eventually) to sustain the cards beyond her death, without needing a successor to her power. Hell, this could have even been a part of Clow's original gambit.
 * Supported by the fact that in ×××HOLiC we find out that Sakura paid her Star Staff to Ichihara Yuuko (the reason has major spoilers for both Holic and Tsubasa Reservoir Chronicle). It doesn't mention what happened to the Cards or Kero and Yue (we may find out once Holic and TRC finally finish up, but this is Clamp), but presumably Sakura wouldn't have let anything bad happen to them. So she may have found a way to support them without the staff.
 * Most likely, the staff is a conduit rather than the source of her powers. While it may have made it easier for her to use them, she was probably able to give it up knowing that she'd still have her magic.
 * Yes, but the staff is also the key to the Clow book. So unless she wanted the Cards running amok after her death, she'd have to change something in Clow's original formula.
 * CLAMP mentioned in an interview in one of the Artbooks that Sakura no longer needed her staff to summon the cards after the original manga series' end (whether this applies to Tsubasa canon, I have no clue). Clow never needed a staff to summon the cards, he simply created one to help Sakura with her growing powers. All the cards can become dormant within the book, storing power from the original owner (as they did with Clow) until they are ready to be used again. Clow always knew Sakura was going to become the mistress of the Cards and knew she would release the cards in that fashon in order to form a bond with them, as mentioned in the end of the manga. When talking about Cardcaptor Sakura and Tsubasa together, I suggest going off the MANGA canon, not the anime, as they missed a whole ton of key points in the anime.
 * Not to mention that when Sakura Kinomoto lends the staff to Princess Sakura in Tsubasa Chronicle, she says "It's alright, I still have the cards with me" (or something to that effect) implying that she could still activate them without the use of her wand.

Naoko had magic powers as well...
Or at least, she was incredibly Genre Savvy. Don't remember Kerberos confirming that she hadn't any magic powers, and she created those things with that card's diary quite too well, perhaps she added a bit of her own magic, unconsciously. Also, it's an unwritten CLAMP rule that nobody that uses glasses can be just an ordinary person (Fuu, Watanuki, Satsuki from X, Yukito and friggin' Clow Reed are fine examples of it). So, her magical powers can be something small, or even God-like ones. (There was another rule for side characters gaining repentine spotlight, but it was a bit less strict than the megane one.)

The entire series was just Mitsuki's fantasy from Full Moon o Sagashite
There are lots of parallels between both series: cute, permanently happy girls with guardian angels doing magical things. Keroberos has a plush toy form, Takuto and Meroko have plush toy forms. Yuki can turn himself into a human, Takuto and Meroko can turn themselves into humans. The whole thing sounds like some fantasy made up by Mitsuki to pretend that she wasn't fated to die. Sakura's guardians even have rivals (Spinel Sun/ Ruby Moon), which are just more edgy versions of Kero and Yue. Izumi and Jonathan, anyone? Sakura's friends still have the generic personalities that Mitsuki's friends have, and Sakura loses a parent (Mitsuki loses both). Mitsuki probably felt left out while her shinigami were defying the laws of physics, so I'm guessing she just imagined that she had magical powers and that the shinigami would help her capture cards instead of capturing souls by themselves.

Tomoyo's mother was artificially inseminated
This one is pretty straight forward: Tomoyo's father is neither seen nor mentioned and Tomoyo's mother could never love anyone other than her (female) cousin. She also has the wealth to easily get a top donor.

Tomoyo is in fact, a test tube baby who was partially cloned from DNA samples from her mother and Sakura's
Related to the above. Since Tomoyo's mother could never love anyone other than Nadeshiko, she decided that if she couldn't have her, she might as well have her child in a sense.
 * So, Tomoyo loves her... half sister? Squick!

Keroberos is an assumed name.
He is not really Cerberus, Hound of the Underworld. Seriously, count the number of heads. Clow summoned Demon Prince Vapula via Ars Goetia. But even some atheists might raise their eyebrow at this, so he gave Vapula amnesia and gave him an "obvious" mythological name. People were too busy patting themselves on the back "Hurr! I know Greek Mythology!" to explore further.
 * Also. "Clow Reed?" Let's look at that through Japanese intonation!
 * 1) Clow Reed.
 * 2) Crow Leed.
 * 3) Crow Li ("Li" being the name that his descendants eventually settled on)
 * Except that the Li clan is Clow's mother's family, which would make 'Li' her maiden name.
 * Also: Clow HAD no "descendants". The Li family are described in the canon as Clow's 'relatives' because his mother was a member of the Li clan, but Syaoran and his lot are not 'descended' from Clow. Arguably, the only one who could really argue to be Clow's descendant is.
 * 1) Crowley.
 * Following this pattern #41 Focalor is a man with wings.
 * Though Keroberos may be a complete mess up of Cherub -> Xerub -> Kerub which are winged lion, men, bull, and eagles.

The Book of Darkness is a Mirror Universe analog to the Book of Clow
Both are deeply powerful magical artifacts that capture portions of a mage's power to be used at the call of a master. The Book of Darkness just got twisted.
 * The Book of Clow is used to store and contain the Clow Cards, which were created by the same person. Its not used to capture portions of a mage's power at all. The Book of the Darkness was designed to collect spells from various sources in order to study them. They're nothing alike.

Since Sakura turned the Nothing to the Hope...
Sakura has effectively stopped the negation of the positive energies of the other fifty two cards. The world can no longer stay stable and will eventually lead to some mass apocalypse. Mayhap this will explored in Chronicles or xxxHolic.

The Hope is, in fact, a less depressing name for The Nothing.
Because the Clow Cards haven't destroyed the universe any time in the next ten years or so, according to Tsubasa Reservoir Chronicles.

The real reason Eriol went back to England? To teach Defense Against the Dark Arts at Hogwarts.
With his vast knowledge of both Eastern and Western magic, he'd certainly be well-qualified, and he does need something to do after he finishes with Sakura. And Hogwarts *always* needs new DADA teachers.

Tomoyo recorded Syaoran's confession to Sakura at the end of Episode 69.
Reasons:
 * She was there with her camera.
 * She was awake.
 * No way would she miss such an important moment in Sakura's life.

Eriol created the design of Ruby Moon and Spinel Sun as homage to Yuuko

 * The logic on this one is pretty simple. Eriol is . Clow Reed was very involved with Yuuko and , so he probably was at the very least a friend and must have known that the butterfly was her symbol. So when Eriol went to make Ruby Moon and Spinnel Sun as alternates to Yue and Keroberos he gave them butterfly wings and a darker color scheme as homage to her. It also explains why, despite being a technically sexless spirit, Ruby Moon dresses and acts the way 'she' does.

Sakura is actually the shojo analogue to Simon.
Think about it. Sakura and Simon both "inherited" their powers/abilities from someone else (Sakura got her magic from Clow Reed; Simon got his Hot-Blooded nature and much of his Heroic Spirit from Kamina). Both of them are trained by their predecessors in the use of said powers/abilities (Clow trained Sakura by proxy of Kero and Yue; Kamina fought alongside Simon as Bash Brothers). Each is a Badass Adorable (Admittedly, Simon only really counts as adorable pre-timeskip). Furthermore, each one has pretty much limitless power/potential (Simon's Spiral Power is infinite by Word of God; Sakura is even more powerful than Clow Reed by the end of the series as a ten year old, there's NO WAY she won't grow stronger). Finally, each gets kind of screwed over in terms of interpersonal relationships - Simon: his first crush falls in love with his bro Kamina, who promptly dies in the next battle, one of his closest friends performs a Heroic Sacrifice near the end of the series, and his wife disintegrates immediately after exchanging their vows, and it's implied that he'll carry that pain until the end of time. Sakura: Well.... For the sake of brevity, just go and look at Cardcaptor Sakura.

Afterthought: Each has Beware the Nice Ones as their M.O.

Clow Reed got his inspiration of creating Clow Cards from the undead
Just that he had to change the pictures of all the cards to avoid plagerism. Said re-edition results in the majority of the Clow Cards being in Bishounen Line.

Tomoyo's mother's company is Piffle Princess.
Let's face it, the products Tomoyo brings out from her mother's company look very similar in terms of design to Piffle Princess products that appear in other CLAMP manga. While Icchan is responsible for Piffle Princess's Angelic Layer branch, there's nothing to suggest that he's in charge of the whole company. It would also make sense, considering that one Tomoyo in Tsubasa was president of Piffle Princess. It would also explain why in later series like Legal Drug Piffle Princess has branched out into clothing.