Saying something about how pretty the dog is helps too. Most find that part hard the first time.

You walk in a room, not any room in particular, just some room. There's a man and woman in the room and they are engaging in some activities where one is wearing a collar and the other is holding a leash. Domination activities that some may find erotic.

Rather than freak out, wonder what they are doing in [room] or taking some otherwise normal course of action, you just walk by, pat the leash holder on the back one time, (One of those friendly back pat/taps, the kind you get from the person that's not your boss but could probably make you lose your job if they wanted to) chuckle and give em the old: "So, who's walking who?".

Then Continue on your way.