User blog comment:ExtremeVelocity/Cameos!/@comment-9877332-20130818103859/@comment-3261234-20130818124721

Hmmmm.....when Yui goes towards the Light Music Club for the first time (first episode), she imagines the members to be scary persons like this. This is an allusion to the character Johannes Krauser II from the anime and manga Detroid Metal City.

I bet there's more, wait a bit, I am going to search...