Proprietor is a type of NPC introduced in the The Sims 3: Showtime. In Late Night, an agent can call a Sim who has created a band and request that the band play a gig in their bar or club; this is similar to a proprietor.
If the lot they're present contains a bar, the proprietor will serve nectar at random, and a Sim can request to buy a round of drinks, a drink for themselves or even for another Sim. Random townies are the only Sims that can work as proprietors. The player can also have their Sim ask a proprietor to land them the acrobat, magician or singer profession.