I was standing next to the ticket counter, in uniform, waiting to jumpseat to ORD. A man rushed up to the counter about 5 minutes before departure time and the following conversation took place:

Pax: "I'm on this flight and I want to upgrade to First and I want seat 3A.
Agent: "Sir, I can upgrade you but we don't have a seat 3A on this aircraft" (It was a 737-300 with two rows in First Class).
Pax: "What do you mean there isn't a 3A on this flight ? I fly this flight all the time and I always ride in 3A.
Agent: Sir, this is a 737 and there are only two rows of First Class seat. I can give you seat 1B.
Pax: "Don't lie to me. I don't want 1B, is there anyone in 3A...just tell me and don't BS about it.
Agent; "No sir. There isn't anyone in seat 3A.
Pax: Good, then quite lying about it and give me that seat.

The agent gives him a boarding pass and he turns to me and says, "Don't go anywhere Sonny. I left my car at the curb and have to go park it".

After he ran back down the concourse, the agent turned to me and said "get your bags and come on. We're out of here". We hurried down the jetway and the agent told the working Captain everyone was onboard, briefly what happened and the Captain said "close the door, we're gone".

That Gentlemen is a true story and kudos to the agent !

G'Day Mates