A cowboy walks into a bar, sits down, and asks for a shot. Across the bar, a Mexican man is sitting and glaring at the cowboy.
The cowboy takes the shot and slams the shot glass down on the counter, yelling "TGIF!"
The Mexican orders a shot, takes it, and slams his glass down, yelling "SPIT!"
The cowboy looks over at him and notices the Mexican guy is still staring at him. The cowboy once again orders a shot, slams it down, and yells again "TGIF!"

Once again, the Mexican orders a shot, slams it down after consuming it, and yells out "SPIT!" This goes on for a while, and the bartender stands puzzled and annoyed.

Finally, the bartender asks the cowboy "Just checking, but do you know what TGIF means?" and the cowboy replies "Hell ya I know what it means - 'Thank God It's Friday!'"
The bartender asks the Mexican guy "Okay, so what does 'SPIT' mean?" and the Mexican replies "Stupid Pendejo It's Thursday!"

~Bill

In my defense, I was left unsupervised...