This dub was an extremely rare crossover – Funimation-originating actors never recorded at Houston-based ADV (though the opposite happens all the time) – Yet Kanon has two: Mishio is far better known for being Luffy, and Kaori was Vivi and Winry (and did a lot of singing for Funi's shows).
Marth Debuted in Smash Bros.: The cast of the show – three of them, at any rate – first debuted in the West in a cameo in Air. It didn't take ADV too long to pick up the KyoAni version of Kanon, but the Toei version had been out for half a decade at that point. And yes, the voice actors are all the same despite a nearly two-year gap between the shows.
No Export for You: The Toei version of the series has never seen the light of day in the West, and the fandom in general seems to prefer to keep it that way.
The train station that plays such a big part in the story is modelled after Moriguchi station in Osaka.
Ayu's winged backpack wasn't actually supposed to be foreshadowing her nature; it just turned out that way. The director told the character designer to take the wings off the backpack because they might count as a spoiler, but later added the wings back on.
No, those two moments in episode two of Kyoto Animation's adaptation are not Haruhi Suzumiya references; they were in the original game. It is pretty funny, though, all things considered.
Shiori's favorite fountain is located in Tokyo's Showa Kinen park, which in real life charges a fee and thus cannot be entered freely.