The Bartender was a Chiss with no name who tended to bars throughout the Force Galaxy. As a Chiss, he lived for thousands of years and had many different jobs. He used to work on the Endar Spire in its Cantina but left due to a weird feeling it gave him (actually a side effect of Trask following Rarth Devan)
Thousands of years later, he was working on Nar Shadda. Kyle Katarn came in asking about his boss who was actually a Reborn. Bartender didn't tell him where the boss was but then realised Kyle was a Jedi, and allowed him through.
He then went on to serve in the Grunt Stop, as a waiter. If he is ever injured, he goes 'Duhuhaah'. This happened several times during his stay and it got so annoying that Jorgey fired him. He tried unsuccessfully to use this Duhuhaah as the basis for a singing career, but that didn't work either. Thankfully, Bartender finally found work running a shop called the 'Buy 'n' Die!'.
Because he is a Chiss, some people refer to him as 'Bartender Chris'. He also apparently has a Brother.