In the movie "Ocean's Eleven", Yen was a 95 pound "little chinese guy", who worked as an acrobat in a Las Vegas show. He was so flexible that he could fold in half and fit in a very small tube in a portable safe. At the time of the robbery this is how he got into the vault of the casino. He got in, and therefore they called him the greaseman.

phone: why don’t you go to sleep tommy it’s 2 in the morning?
tommy:why don’t you die you dumbazz

man look at that guy raping his dog I bet that's Grease man