The Haruka who brings misfortune.
Little Busters: Saigusa Haruka has been treated by her family as the source of all bad things that happened to them.
Rewrite: Asahi Haruka, the cursed girl. She brings death upon people around her. Anyone who talks about her will be cursed.
Both heroines had a tough childhood due to their ‘curses’.
Though this is probably unintentional.
(rewrite/AIR spoilers)I think the Gao t-shirt isn’t just an accident. Both worlds have a lot in common… except for Maeda as a writer (but he was quality checker or something like that).
It is my hunch that AIR has a special place in Maeda’s heart because of two reasons: he wasn’t satisfied with the ending of AIR (people didn’t really get) and the worlds are quite similar.
Maybe… there would be a hint of a third core/series in the anime. daydreaming off Also don’t forget about the little crossover in the manga. i know I know… but then, who knows? 
Just saw this on twitter:
Kanako from Tomoyo After in Clannad!
I could have sword I mentioned that…
…
Welp, that’s the most nondescript post ever.
What do you read Makoto ? Oh, the manga “Key” ? Good choice !
(Kanon 2006, épisode 5)
Air cameo in Clannad.
Have you seen this guy? (a.k.a. Yukito-san).
Seen on season I, episode 6, near the end (around 20’).
#######yukitosanmemories
More self references… 
These contains spoilers about Rewrite (vn) and Air (anime/vn). You’ve been warned.
This is a reference and maybe much more.
Make your own conclusions.
Remember: she wears some well known t-shirt at some moment…
Another similitude with AIR: Kotarou left her at some point, late in the story.
It makes me wonder, and speculate a lot, if Rewrite is a real ‘canonical’ pseudo-sequel, or if all of this is just a heavy reference/tribute.
We have talked about this before, but we haven’t come to a conclusion yet.
There was also a Saito in Charlotte
Interesting…
I am going to be playing through Air and am currently playing though Rewrite, I will keep my eyes open for any references there as well.
Rewrite didn’t have anything written by Maeda so I don’t think there’s a Saito there.
I don’t know if it was already mentionned earlier in here but Rewrite Side-R seriously had lots of references. There was a Dango Daikazoku logo on that box Chihaya held when she first appeared, and Kotarou found a magazine titled “Masato’s muscles or something” when he looked for Kotori in the forest (in the beginning) and remember that guy who controlled a puppet and made Akane spit the juice she was drinking?, they made sure that he looked exactly like Yukito, the puppet too. There’s also an OMAKE in one of the volumes where the heroines wore the other Key uniforms. If I remember correctly, it was like this: Kanon’s for Kotori and Air’s for Chihaya (or the opposite, I don’t remember that well), Clannad’s for Shizuru, Little Busters for Lucia (she wore it exactly like Kurugaya just so you know) and Angel Beats’s for Akane (no, not the school’s but the after life battle front or whatever is its name). There were other references but I have to read it again to find them.
Oh that’s pretty interesting! I’ve never read Rewrite Side-R nor Side-B so it’s fun to see them do that sort of thing.
Heck, I’d say that Rewrite in general has the most self-references out of any other key work
I knew I remembered those names from somewhere!
Although this is still both Rewrite related, they referenced the seperate SiglusEngine benchmark they made for Rewrite, in the anime! It’s was a program that tested if your computer is good enough to play Rewrite.
Rewrite Anime, first episode. In her introduction scene, Chihaya says “Auu”, just like Sawatari Makoto in Kanon, who Chihaya’s design was (probably) inspired by.
Don’t forgot the legendary cafe Key.
I FINALLY got around to playing Clannad, and saw this:
