Mundo is the Spanish, Filipino, and Portuguese word for "world".
The icons for Dr. Mundo's Burning Agony and Masochism skills used in game on the champion info screen show him in his original model, which was used in the early closed beta. In fact, we can see that model on a coffin of Voodoo Shaman in Autumn version of Summoner's Rift.
His /dance was inspired by TV series House, M.D., from this episode where Dr. House dances to the song "Fight The Power".[1] A side-by-side comparison be be seen here .
According to Rinoa, Dr. Mundo's first name is Edmundo, named after an artist at Riot.[2]
Mundo is apparently lactose intolerant, as said in this post.
Dr. Mundo is one of the five champions who use health as a primary resource for casting spells. The other four champions are Aatrox, Mordekaiser, Vladimir and Zac.
Quotes
Dr. Mundo's quote "Mundo...mmm...*slurp*...smash!" may be a reference to the Hulk, a Marvel Comics character.
Dr. Mundo's famous quote, "Mundo will go where he pleases." may be a reference to Duke Nukem's quote, "I'll go where I please, and please where I go." This quote is also popular in the League of Legends community.
For Dr. Mundo's Corporate skin, many of the quotes are references from various office comedies, such as from the movie Office Space.
The quote about the mail room may be a reference to the Broadway musical How to Succeed in Business Without Really Trying, where the main character starts off working in the mail room like one is supposed to in business.
The quote about the ABC's of Mundo - "Always be cleavin" - is a reference to Glengarry Glen Ross where Alec Baldwin's character explains that a good salesman should "always be closing."
The line "PC LOAD LETTER? What the Mundo does that mean?" is a reference to the comedy film Office Space.