Do you have anything prepared for this? Do you say, no but come back in a week?
Do you say, yes, here are four pre-gen character sheets, let’s play a random short one-shot?
Do you say, no we’d need to spend time prepping for D&D but here’s a simpler tabletop game which uses minis and dice, let’s play this right now instead? (for example, Shadowdark)
Or something else?
I wing it. You know that sensation of DM scrambling you feel when your party goes off the rails and is somewhere doing something you never expected?
I just DM a short session in that way.
I tell them what they are, race/class wise, then ask them to think about what kind of person this is, and to act like that person. I don’t use sheets, just scrap paper and some dice, and the plot that I take them through is probably going to very closely resemble an episode of a show or the intro to a movie I’ve watched recently. I follow the actual rules insofar as they are convenient, but what I’m really doing is just trying to show them what role playing feels like.
Nice! That sounds perfect.