For April Fool's, the original Classic skin artwork used to have the deceased champion Urf, the Manatee, who could be seen at the bottom left of the artwork.
Traditional Lee Sin resembles how he looked before his official release (seen in the second official trailer). Click here.
He can be seen at around 0:11, between Jax and Teemo.
Dragon Fist Lee Sin (Lunar Revel 2012 event release) skin is a tribute to Bruce Lee, the famed martial artist/actor of 1970's action movies. The skin seems to be specifically referencing his trademark look first seen in Enter the Dragon.
Dragon Fist Lee Sin's idle animation is Bruce Lee's move when serious.
Muay Thai Lee Sin was created to celebrate the launch of League of Legends in Thailand and pays homage to Muay Thai, a combat sport native to the country.
Muay Thai Lee Sin is the third non-legendary skin to have a different dance animation from the original skin, prior being Jurrasic Cho'Gath and Dynasty Ahri.
Lee Sin was once a summoner-in-training at the League, before committing a devastating incident which left him with profound guilt. After the devastating incident, he traveled to the Shojin Monastery in Ionia in order to repent, becoming a brethren to the monks there.
Lee Sin's former mentor was High Councilor Reginald Ashram, the first leader of the League.
Lee Sin has a sister from the now liberated province of Galrin.
Lee Sin did an interview with L. B. Briskes on a raft over Lake Contemplation.