In Mexico City's slang, a big wig or big shot is referred to as caca grande, which literally means "big shit." The stereotypical caca grande is despotic and rude to those that are powerless.
When somebody gives him or herself a lot of importance (in other words, want to pass as a caca grande), a Chilango might tell him or her ¡has de cagar muy ancho!, which literally means "you surely defecate thick turds." This is a reference to that person being a caca grande (the connection should be obvious).
Back in the 1970s Los Polivoces (two old school Mexican comedians) created a character that colorfully portrayed a typical caca grande: el Mostachón. He was the CEO of a company and was always ignoring, mistreating and scamming his employees, one of which was his friend el Washanwear.
Below is a poster of a movie that shows el Washanwear (left) and el Mostachón.