What was the relationship between Steve, Fischer, and Fischer's sister?

Question

In S3E10 "Lois' Makeover", Lois starts wearing heavy makeup after a poor performance review. However, at the end of the episode, a man sees her in the parking lot and asks "How much? Is it cheaper if we use my car or do we have to get a room?" Lois takes the man to her boss Fischer as proof that her makeup is excessive and she is performing acceptably.

After Lois leaves, Fischer says to the man:

Well, Steve, are you going to tell my sister or should I?

Clearly this is intended to be some hilarious coup de grace joke, but I've never understood it. It tells us that:

• Fischer and Steve know each other
• Fischer's sister is involved somehow

But I can't figure out anything beyond that.

Answer 1

The joke/point here is that Steve has mistaken Lois for a prostitute and Fischer is taking Steve to task for propositioning a supposed hooker.

The punchline is that Steve is, apparently, Fischer's brother-in-law and so Fischer feels compelled to ensure that his sister knows the truth about Steve.