Like all my careers this requires the XML Injector.  I've read that Bartenders / Mixologists are buggy, so naturally I was intrigued. Since you encounter them all the time I did want to try and make them definable. As it turns out they aren't buggy. They're the deepest, most thought out NPC career I've encountered so far! Each bar draws from it's own world's population and has it's own shift. That's why it might seem buggy; if you define just one bartender he won't show up in another region at all - and it's by design.

Well I take all that and toss it out the window! Because I WANT to make this career draw from a small pool of Sims defined by me. Interesting note: if you want careers defined by venue to work have the venue xml come before the company xml in the appropriate place.

Note that the following jobs have their own uniform and overrides a custom one. So, if you have a particular character you want in there to use a custom outfit (like a distinct robot or the social bunny) maybe play it with an Outfit Lock trait.
Relaxation Venue
Selvadorada
Batuu
Black and White Party
Moonwood Mill
Sixam (no uniform)
Henford-on-Bagley (no uniform)
Sixam (no uniform, alien form)
All of these retain their situation outfits. If you want a particular chatacter to be a character with a costume during these events, you may want to use my Outfit Lock trait.  i haven't really tested out different situation, however. There's a million of them. Every one is uniquely defined! I may need to update this mod at a later point just for a new, minor, festival.

On that note: Sixam bartenders requires aliens. Although in one test one Mixologist was turned into an alien for that event, so ... that was interesting.

Unlike every other NPC career so far Basegame Bartenders do not require a specific trait.

Werewolves

Despite the XML looking the same this venue behaves somewhat differently the regular bar venues when it comes to the company names. So, when you apply the trait from the rewards panel it will bump you into the career every time your Sim is loaded. I had tried to make it function like the Basegame Bartender career, but it wasn't happening.

Being Greg will turn your Sim into a werewolf when his signs are interacted with. In addition other Sims won't be able to interact with them much. My Reaper Actions Unlocker has a Greg component that takes away much of Greg's Greg-ness if that's what you want.

To note: As usual, I've allowed teens to do this job and have removed all filters. The job originally filtered out Sims without a minimum of 3 in the Mixology skill. But it's up to you. If you want to have an incompetent barman I won't stop you.

NPC Bartender Careers + Werewolf NPCs