One of my favorite Mexican expressions is often used to describe someone who thinks extremely highly of himself: él se cree la última Coca-Cola en el desierto ("he thinks he's the last Coca-Cola in the desert"). Not long ago I was in Oaxaca, and on a very hot afternoon, this enterpising horchata salesman had appropriated the phrase to move some of his wares, a creamy rice-milk drink.
Wise guy in Oaxaca
in Mexico City