Suzumiya Haruhi, is an intelligent high school girl with a mischievous personality, and very egocentric disposition, and upon enrolment at school she announces:

"I have no interest in ordinary humans. If there are any aliens, beings from the future, or super-humans, come see me. That is all!"

Naturally, this did raise a few eyebrows, but Haruhi is dead serious. Things get awkward when everyone realises just how serious she is about it all and establishes the SOS Brigade. What makes her quite ominous though is her unimaginable power to actually change the world, but she is totally unaware of her own power and so she is also unaware of the affect of her power on the outside world. The cynical Kyon, a friend at the SOS Brigade, is among the few who knows of Haruhi's power, and is desperately trying to keep the world together.

[Source: AniDB]

A parody series featuring the entire cast of The Melancholy of Haruhi Suzumiya in a smaller form factor. Among the changes are: Yuki plays eroge, Haruhi is even more obnoxiuous and loud, Mikuru is even more emotional and Koizumi harbors a deep love for Kyon. Kyon, on the other hand, is generally the same as ever.

Suzumiya Haruhi is a charismatic high school girl with a carefree personality and a very egocentric way of thinking, that she underlines upon enrolling at school by announcing: "I have no interest in ordinary humans. If there are any aliens, beings from the future, or espers, come see me. That is all!"

This makes quite a few heads turn, but Haruhi is dead serious, as she soon proves by establishing the SOS Dan.

As it turns out she has the unimaginable power to change the world, but is completely unaware of this power, and so she is also unaware of the effect her power has on the outside world. The cynical Kyon does not become Haruhi's best friend and first member of the SOS Dan out of the kindness of his heart, but initially out of self preservation, since he quickly understands the possibly catastrophic implications of Haruhi's powers. Luckily he seems to have the gift to keep her more outrageous schemes in check...

[Source: AniDB]

It is mid-December, and SOS Brigade chief Suzumiya Haruhi announces that the brigade is going to hold a Christmas party in their clubroom, with Japanese hotpot for dinner. The brigade members Kyon, Nagato Yuki, Asahina Mikuru and Koizumi Itsuki start preparing everything for the party, such as costumes and decorations. But a couple of days later, Kyon arrives at school only to find that Haruhi is missing. Not only that, but Mikuru claims she has never known Kyon before, Koizumi is also missing, and Yuki has become the sole member of the literature club. The SOS Brigade seems to have never existed, nor has Suzumiya Haruhi. No one in the school has ever heard about her... except for Kyon.

Now it is up to him to travel back through time to find Haruhi and correct the temporal anomaly.

[Source: AniDB]

Shy, awkward Yuki Nagato attempts to court her crush, Kyon, with the help of her best friend and neighbor, the perky and indomitable Ryoko Asakura. Together, the trio defends their high school literature club from extermination…and from the pestering of their over-the-top classmate Tsuruya and her friend and minion Mikuru.

[Source: Crunchyroll]

OVA bundled with the 9th volume of the Nagato Yuki-chan no Shoushitsu manga.