On a southwest flight:

Guy: I’m seat C21.
Me: What?
Guy: C21, it’s my seat.
Me: No, that’s your boarding position. You can sit in any seat.
Guy: Really?
Me: Yup
Guy: I wish I’d known that before I came back here.
Me: …
Guy: Well, I need the aisle seat, can you move?
Me: …
Guy: …
Me: Nope.