After disguising Maria in a nurse's outfit, one of the Sanzenin SP's says the phrase "The sister is more important than defeating Britannia". This is a reference to the series Code Geass.
After Nagi had said that Café Donguri would go out of business, Hayate says "even though we're going through some tough times, the comapny as a whole is still profitable". In this sequence a SonyPlayStation 2, PlayStation 3 and a PlayStation Portable can be seen.
Having been asked by Ayumu if she was working because she was bankrupt, Nagi callously suggests that she'd buy the three publishers of One Piece, Conan and Zetsubou-Sensei and serialize them in one magazine . This is a reference to the three publishers Shueisha, Shogakukan and Kodansha.