- Completely Different Title: "Dan et Danny" in France; "Kate & Julie" in Italy — because Kei sounds like "Chè" ("What?") in Italian
- Development Hell: The anime series was stuck in conceptual stage long enough that when it finally went into production, it was late enough into the year that episodes 25 and 26 would have conflicted with major christmas and new year programs, so they were dropped. They would be released later as OVAs.
- Fountain of Expies: The two title characters, who compose of a Tomboy and Girly Girl pair, the tomboy usually having short reddish hair (though it can be long or just lighter colored hair in general as well) and the girly girl having long, more feminine hair (and like with the tomboy, can also be inverted as having short, yet dark colored hair). Three of the best-known pairs, that are often thought of as being the best-known direct expys of the two, are:
Trivia / Dirty Pair