This is the first thing that sprung to my mind:
Sayonara Zetsubou Sensei, Chapter 9
Take a look at the third panel. Here, a young illegal immigrant is listing things which show how nice the Japanese are - one of these things being that they cry over songs with "no substance". And gee, that A-symbol on the CD case certainly looks familiar...
Edit: Now that I think about it, Ayu was also referenced in Azumanga Daioh, when one of the leads (Tomo) got a haircut and said it was "to look like Ayu" or something like that.