Tepoztecatl is famous as the Aztec god of pulque and by extension all alcoholic beverages; he has power over anything containing alcohol. In Aztec myth, he's one of the Centzon Totochtin, the "400 rabbits," children of Mayahuel. In Wapsi Square he's currently living with Monica and Dietzel in Minneapolis.
Tepoz is also a prototype golem created by Mayahuel, the only known golem who has no memory of a prior human life (he suspects he was some small expendable animal when alive). When the Chimera was split into the three Golem Girls he was given the 'honor' of being their keeper.
For an unknown time he was dormant in the form of a small statue until Monica unintentionally reactivated him. It was Tepoz who brought the Golem Girls to Monica, although it took her a while to warm up to them. He's usually somewhere around the museum or Monica's house these days.