Although design-wise there is no clue that Maokai is an Oriental character like Xin Zhao. His name follows the Mandarin pinyin scheme like Xin Zhao (while Lee Sin's name is of different scheme). The official Chinese vendor translates his name as 茂凯 which literally means "lush (vegetation)-triumphant".
Maokai was originally intended to be just a Support/Tank when he was first released however it was realized that Maokai made a better Jungler with strong ganking capabilities.
The rune spiral that is on Maokais' ult is the same rune that is attached to Xerath's chest.
His /dance is a reference to the Harlem Globetrotters.
Maokai's ability Sapling Toss is a direct refrence to the game Pikmin from the toss to the sapling's sounds.
Maokai shares a place with Poppy in having the highest base armor of any champion at level 18 (90 armor).
Skins
Totemic Maokai is based on a totem, which is an animal or other natural figure that spiritually represents a group of related people such as a clan.
Festive Maokai was only available during the Snowdown Showdown of 2011.
In the picture frame on Festive Maokai's artwork, the Snowdown Showdown art for 2011 can be seen
Haunted Maokai was only avaliable during the Harrowing of 2012.
Haunted Maokai resembles part of a reanimated Graveyard.
Haunted Maokai and Zombie Brand are the first skins that have animation on respawn.
Relations
Maokai is a tree from the Twisted Treeline that has become animated. He despises the existence that was thrust upon him as he felt it was a corruption of nature and so fights as a soldier of nature.
Maokai despises humans and their chaotic use of magic.
Although Maokai and Malphite have different attitudes regarding their being brought to life, Malphite stated that he is "...proud to call the Twisted Treant my ally", suggesting that these two elemental champions get along quite well despite their differences.