Amumu was one of the champions available for the Ionian pool during the Ionia vs. Noxus match, and was one of the selected champions.
Amumu is the third champion to have 7 skins.
Amumu's dance is a reference to the television show South Park, in which the Gothic kids would dance by shuffling from side to side, and take a smoke from their cigarette every second time they turned. A side-by-side comparison can be viewed here .
Both dances are, in turn, parodies of the classic "Peanut's Dance", which is the bizarre shuffling dance performed by the characters of the Peanuts comic.
In the Emumu skin, the background posters are a parody of several well-known bands: "Death Cab for Corki" for Death Cab for Cutie, "Cho'Gath Eat World" for Jimmy Eat World and "Anivinescence" for Evanescence. The "sad-face poster" is a parody of Blink-182's "symbol which is a happy face."
In the background of the Chinese Emumu skin, a ghost Tristana is playing a bass and a ghost Poppy is playing drums.
The Classic Amumu artwork is used by The Tribunal to indicate an error.
Little Knight Amumu is a reference to The Sword in the Stone from Arthurian legend, only instead of removing the sword from the stone, Amumu breaks it.
The skin was an idea from the Riot staffer Nikasaur, her first skin idea, as revealed here
In the Chinese artwork, Amumu is shown with the sword in one piece, and he wields it against Warwick. If you look closely behind him, you can see a passed out girl that bears a strong resemblance to Annie, one of his close friends.
Sad Robot Amumu might be a reference to Marvin the Paranoid Android of the novel: The Hitchhiker's Guide to the Galaxy. It also bears a striking resemblence to Robot Jones off the show "Whatever Happenned To Robot Jones". It might also be a reference to Chibi Robo, due to the outlet that he drags along
The skin's laugh was bugged upon release and could be heard globally by both allies and enemies. This however has been fixed.