I've noticed that there have been 'Chobits' cameos in other stuff made by Clamp so I decided to make a topic about it.
First of all, I read that in an episode of 'xxxHolic', there are earmuffs that appear which look identical to Chii's ears. I haven't seen 'xxxHolic' yet but I did read about that in an issue of 'Anime Insider'. I saw the first episode of 'Tsubasa: RESERVoir Chronicles' and Chii appeared in it but it didn't seem like the same Chii as in 'Chobits' and one Wikipedia, I read that Sumomo, Kotoko and the Landlady have also appeared in the series. Last but not least, I saw the second Clamp crossover music video called 'Clamp in Wonderland 2' and there's a part where Chii, Hideki, Sumomo and Kotoko dance to the song. You can see it on YouTube. Here's the link.