So I've been rewatching Lucky Star since it's filled with references to other anime and then this happened. I came across the episode where Konata is trying to come up with a nickname for Kagami, and one of her nicknames is Kyou, as in Kyou from Clannad. The actual explanation was something about the mirror image of the kanji of Kagami is Kyou....or something. I don't know Japanese. Then it struck me that the Hiiragi twins are VERY similar to the Fujibayashi twins in Clannad, down to the hair color and personalities. Then it totally blew my mind because Clannad came out AFTER Lucky Star. They're referencing stuff that hadn't even come out yet!
Have you ever considered the reverse might be true? That Clannad had those characters as an homage to Lucky Star?
Maybe. The converse of that statement might be true seeing as how the Clannad visual novel (2004) and manga (2005) were released well before Lucky Star (anime) was created. Only the anime (Clannad) was released after. Except that the Lucky Star manga was released in 2004... So yes, I guess your statement could be true. If Clannad were referencing Lucky Star, then they would be referencing that specific scene I mentioned between the relationship of Kagami and Kyou. I'm looking up when Clannad (visual novel) was released and according to Wikipedia, Apr. 2004. Lucky Star's manga was released in Jan. of the same year. Wow. They were released 4 months apart. So it would seem that Clannad pays homage to Lucky Star after all. Still, the name relationship is ridiculous.