Carmelita: Freeze, raccoon!
Sly: How can I freeze when my heart warms at the very sight of you?
― Carmelita and Sly conversing in the Kunlun Mountains[src]
Sly climbed to the top of a building where Carmelita confronted him. She believed Sly was up to no good, but he tried to reason with her that the person he was stealing from was the notorious Panda King, a pyromaniac bent on developing a new firework technique. She ignored his comments and chased him through a long passage of Chinese homes and training facilities, around a giant, magnificent gold dragon statue. When Sly reached the tail of the statue, he launched some fireworks at the dragon's head, sending Carmelita away yet again, allowing Sly to take the treasure key.
Multiple blood vessels burst in my brain while figuring this out. The code had better be... 2-3-1.
If all other vaults are unlocked first and Clockwerk has not been defeated:
Unfortunately, this vault code appears to have been written in owl dialect. I won't be able to crack the code until we meet and defeat the bird who created it.
Behind the scenes
In the PAL version of the game, the bonus commentary is removed from this level.