His quote "Mess with the bull and you get the horns!" may be a reference to the Breakfast Club. Said by principal Richard Vernon: Don't mess with the bull, young man. You'll get the horns.  A side-by-side comparison can be seen here .
The Golden Alistar skin may be a reference to the Biblical golden calf.
In his Chinese artwork he has four fingers despite his model only having three. It also shows him having three knuckles (suggesting four fingers) in his classic, black and golden artwork. It corrects this in the Matador Alistar, Unchained Alistar, Longhorn Alistar and Chinese Golden Alistar artwork.
In his Original Splash Arts, he has 3 fingers.
In his Chinese Longhorn Alistar and original skin he still has 4 fingers.
There was originally a bug that the Longhorn Alistar texture would all turn blue, this was however later fixed.
The Unchained Alistar skin is free and obtainable by visiting the Riotgamesinc channel on Youtube and then syncing with the appropriate LoL website. If you do not have the champion, Alistar will be given to you for free along with the said skin.