MM! (TV)

In the 2nd opening song, a cameo appearance of anime figures, from the left is Black Rock Shooter and the right is Hatsune Miku, at the back of Manager Domyoji

On episode 9, at 2:49, there is a girl at the festival who resembles Hatsune Miku, though she is a different color scheme, and she holds a stick instead of a leek.

Mio's fanclub could possibly be a reference to K-ON! where Mio in K-ON! had her own fan club. Ayana Taketatsu ironically vocies Azunyan in K-ON!, in which she is often portrayed as a cat, whereelse her version of Mio in MM! is scared of cats.

At the end of ep 12 and the 2 following specials, previously unseeable panty shots are now viewable... probally as a bonus at the end of the series.

On Episode 8, from 15:49 to 16:15, Taro and Tatsukichi while in their cross-dressing alter-egos called each other "Oscar" and "Andre" twice. This may be a reference to the manga, The Rose of Versailles(the protagonist of the said manga also wears the clothing of the opposite gender).

In Episode 5, after Tado Saro called Mio Isurugi with most insulted quotes, the belt increased it's usage and Taro transformed, his transformation scene is a parody of a Super Saiyan transformation from the anime "Dragon Ball Z/GT"

In Episode 5, Mio's outfit at the beginning is the revamped of school female uniform in Zero no Tsukaima.

In Episode 6, at 4:13~4:41, Mio is wearing one of the costume is a parody of a costume weared by Sheryl Nome from the anime "Macross Frontier", except the difference is her color

In episode 7, around 20:05, Himura is seen saying "Loli!" multiple times as he powers up. This is reference to Dio Brando's finishing move from Jojo's Bizarre Adventures known as the popular internet meme "Za Warudo/WRYYYYY"

In Episode 9, at 4:36~4:52, Kirino is holding a pillow with a whole image of Ruri Hoshino from the anime "Martian Successor Nadesico" and Manager Domyoji took the pillow and hugged.

In Episode 9, at 10:58~11:02, an eycatched cameo appearance of Ruri Hoshino from the anime "Martian Successor Nadesico" and manager Domyoji tried to catch her but Tarou Sado stopped him.

In episode 9, in the same scene as the alternate hatsune miku (with black hair and a stick instead of a leek), a man with a star head can be seen in the background. This is a reference to Hoshii from Arakawa Over the Bridge. The yellow rat like suit in the same scene is likely to be a reference to Pikachu.

In Episode 12 around 8:05, the guy buying a cake and spare ribs is holding a Nozomi doll. That is a reference to a character named Nozomu from Kanokon who is wolf girl just like the doll and also likes to eat spare ribs.