From time to time, Saturday Night Live (and also Jimmy Fallon properties and, presumably, other variety shows filmed with a studio audience) will do a bit where someone in the audience interacts with the host. Almost always, that person will be another actor, one of the show’s writers, etc., and not an actual audience member.
What happens to that seat before & after the bit? Is it just empty until needed for the sketch? Does the original occupant get temporarily evicted for the bit, and then get his seat back?