WMG / AIR

Plot

Kanna wasn't the last winged being.
Think about it: Yukito's pseudo-Unwanted Harem all dreams of flying. Minagi specifically says that she feels like she had wings and then lost them. Kanna usually shrunk her wings and hid them under baggy traditional clothing, and Michiru's existence shows that other spirits can take a completely human form. Therefore, due to the veneration-imprisonment of Kanna's family, the others became humans and hid among the populace. Minagi and Kano are their descendants, the wings bred out of them over a thousand years.
  • Adding to this theory, Ayu is also descended from the winged ones. Remember the pink wings she had in the Spoiler Opening of Kanon?
The monks who place the curse are being punished by being trapped in their current incarnations for eternity.
Karma Houdini Warranty, if you will. Since the curse of endless suffering goes against Buddhist beliefs, then the gods would undoubtably be unforgiving of what the monks done, so they figured the monks shouldn't deserve to ascend to the next stage of their souls' journey. SO they gave all those monks Complete Immortality, making it so they couldn't die from any cause; they would even survive the complete end of the universe! Any good deeds they do now wouldn't matter because they wouldn't have a next plane of existence to be judged in, and their lives would now be meaningless. They are now walking the Earth under different aliases each time, being tortered by their bitter resentments, but there's also the possibility that they could truly understand how wrong they were and would see the beauty of life that Mizusu managed to see for herself during her lonliness and brief bonding with her Mom. Who knows, they could be one of the people in the background in the show and other Key properties. Some of them could have even met and befriended Yukito.

Characters

Misuzu was Donna Troy in her previous life...
Or in an alternate universe. Their curses are similar enough for this to work (the differences would be due to oriental and ocidental settings, thus, making the AU part work way better), and one hell of a Tear Jerker.

Sanae is friends with Akiko.
Sanae once manages to make her infamous bread worse by adding a special (yellow) jelly made by "a friend", and who makes an infamous yellow jelly?

Haruko Kamio is related to Akio Furukawa.
Cousins maybe? While watching Air, the two of them kinda struck me as having rather similar personalities/roles when interacting with the protagonist, and the two of them have similar hair coloring (though Haruko lacks the Furukawa hair-tannae). Plus, it's a fun way of tying the series together with Clannad in a weird way.

Misuzu reincarnated in Eternal Fighter Zero.
After Misuzu's death, the story ends with the implied Hope Spot that she will get the happy life she deserves next time she reincarnates. In EFZ she looks pretty happy, and having fun with the powers and fighting skills she received in a world where several girls are fighting for no apparent reason other than just probably having fun.
And considering that several of the girls in Kanon also had to endure similar obstacles... Sayuri, for example, is a Stepford Smiler whose brother died, ans she herself tried to commit suicide; and Nayuki's mom Akiko, in one occasion, suffered a car accident, and Nayuki blamed herself for that; they all received powers and fighting skills in EFZ, and are seemingly having fun fighting (Sayuri looks genuinely happy with her Magical Girl powers, and Nayuki is a powerful Kick Chick when awake, as well as an unpredictable and fun character with her sleepy boxing style), so it's fair that Misuzu, who had it as hard as them, or even harder, gets a second chance so she can be happy.

Possible crossovers

There are three Seasonverses, but they commonly come in contact with each other.
AIR, Kanon and CLANNAD all seem to operate under the same rules. Ayu, Makoto and Nayuki appear in AIR when it couldn't possibly be the versions of them that appear in Kanon, but in the crossover manga, the real ones show up in Kasumi. Therefore, the three worlds are Alternate Universes, but, possibly due to the magic infused in all three, their borders are constantly fluctuating.
  • It also wouldn't be surprising if the CLANNAD characters are counterparts of the Kanon characters, although, unlike their versions in AIR, they are not identical.
    • And how! Maybe: Ayu is Fuko, Nayuki is Kotomi, Makoto is also Fuko, Akiko is obviously Sanae, Kaori is Tomoyo, Shiori is Nagisa, Yuuichi is obviously Tomoya. Kotomi and Tomoyo are the two facets of Mai's personality, and Sayuri's closest Expy, sibling-related-issue-wise, is Tomoyo, since Sayuri's brother died, and Tomoyo's almost died.And of course, nobody could probably replace the Fujibayashi twins.
    • Except maybe Kagami and Tsukasa, but that's another thing altogether.
    • Look at this.
http://tvtropes.org/pmwiki/pmwiki.php/WMG/Air