Upon [legally] releasing some pressure from a car's (model year 2000) over-charged AC refrigerant loop that uses R-134A refrigerant, some of the released fluid surprisingly stayed liquid at room temperature. It is indeed some sort of clear oil, although it smells odd, like it could contain fluorine. Is it normal for air conditioning loops to contain oil in them? Does R-134A nominally contain some sort of oil required by the compressor or other component, or something to enhance condensation? Or does this indicate failure of a component? I would think that a refrigerant loop should only contain things that are gaseous at room temperature and pressure.
Yes there is oil in the system to keep the compressor lubricated. It is carried throughout the system in the refrigerant. It is usually added in when the system is charged.