Adaptation First: The anime and manga were licensed and began release in English before the first novel was translated (about two years before and about half a year before, respectively).
Averted with Disappearance, the translated novel being released in November 2010 and the dubbed movie in Summer 2011.
Also (barely) averted with the Manga adaption too, the story covers Volumes 7-9 with Volume 9 being released weeks before the movie.
Image Song: Every named female character (plus Kyon's sister), Kyon, Itsuki, and Taniguchi have either one or two, plus a personal rendition of the Dancing Theme (though not Taniguchi, who was second season only). It's a little ridiculous.
Their classmates include Belldandy (Bridget Hoffmann/Asakura), Fuu Kasumi (Kari Wahlgren/Tsuruya, as well as Kyon's sis), Donatello (Sam Riegel/Taniguchi), Jim Hawking (Brianne Siddall/Kunikida), Henry Wong (Dave Wittenberg/President of the Computer Club), and Starfire (Hynden Walch/Emiri).
Keep Circulating the Tapes: The 2004 manga was only released in Japan, and only saw a limited print run, to where a physical copy is hard to find even with the help of the internet. The artist of this particular iteration got fired, either due to the artist drawing and selling unauthorized Hentai for the series he was drawing for, or the artwork seen in this series being less than stellar (most likely the latter). Either way, the publisher would rather forget it ever existed, going as far as to commision a completely new manga series to another artist rather than reprinting this one once the Anime got popular.
What Could Have Been: Originally, Kyon was going to be an esper, but Tanigawa felt that Melancholy worked better with him as an ordinary student.
Dub only: For the second season's Endless Eight arc, Bandai considered turning it into a Gag Dub, with the voice actors switching characters, or doing each episode with a different accent. Unfortunately, they decided to do a straight dub instead, even though Crispin Freeman gets to improvise some lines.
Officially it's The Disappearance Of Haruhi Suzumiya in the English market; Japanese materials, however, are inconsistent on whether to use "Disappearance" or "Vanishment" as the translation.