Mayo Chiki! (TV)

Episode 9: Ako and Riko from Kiss x Sis appear named as "Milk" and "Choco".

In Episode 4, at around 10:37-10:40 during the first eyecatch, Subaru says "Ecchi nano ha ikenai to omoimasu" / "I think that perverted thoughts are bad" / "I don't like perverted things". This is a reference to the maid character Mahoro from the anime Mahoromatic, as that phrase is Mahoro's signature catchphrase, reflecting her open hostility to perverted things.

In episode 7 during the beach sequence, the weapon behind Konoe's back is the Excalibolg; the very same bludgeoning weapon used by Dokuro Mitsukai from the series Bludgeoning Angel Dokuro-chan.

In Episode 8 at around the 10:10 mark when the characters are looking for Subaru you can see Danny Choo character Mirai Suenaga in her orange school uniform with familiar cross hair pins and braids, eating cotton candy with her head turned towards the camera.

in Episode 8, at exactly 01:25, you will hear Nakuru Narumi shout "I can fly!" this is the same phrased that used in Denpa Onna to Seishun Otoko when Makoto and Erio where shouting "I can/can't fly!" when they where sent flying in mid-air when they're bike crashed in the fences of the cliff

In episode 9 around 7:44 into the episode, Mirai Suenaga, a Danny Choo character, walked into the butler cafe that Subaru was dragged into. Also, Danny Choo made an honorable mention about the scene in his website.

In Episode 10, during the first few minutes posters from Kämpfer and Hidan no Aria can be seen on the walls of the clubroom.

In Episode 10, a woman in a white dress is seen on top of the roof of Masamune Usami's apartment building. The weird thing is what is she doing there, is she a jumper (suicide) or what?

In episode 13 where Nakuru sells her BL manga, Masamune and Kureha are dressed as Natsuru Senō from Kämpfer (complete with Tora Harakiri stuffed toy) and Aria H. Kanzaki from Aria the Scarlet Ammo respectively.

In episode 13 where Nakuru visits a game shop, you can see a poster of Fate/Stay Night on the shelf nearest to her face. (13:09)