Parts of Chapter 1 show a sense of humor from the author. Where is the humor?

Artemis is quite often witty and sarcastic. Here in Chapter 1 the reader encounters some of that. When he tells Nguyen that "A ragged apron does not a waiter make," for instance, the reader can see his sarcasm and wit. He tells Nguyen that Butler has many weapons but needs only one to kill him. Artemis makes a joke about gold at the end of a rainbow and he even comments that he made a joke. He "almost" chuckles. He also notes when he is finished with the sprite that "a hundred years of alcohol leaving a body by any means possible is not a pretty sight."