Middle seat? What's that? The last time I sat in a middle seat was PHL-ORD on an American Airlines 727, in April 1991. I stood in the back and chatted with the FAs for over 90 minutes of that 2 1/4 hour flight.
As you can tell, I don't do a lot of last minute work travel.

Actually, I came very very close to getting stuck in a middle seat this past weekend due to a cancellation. If I didn't need the RT flight segments to make UA 1P, I would have just asked for a refund and driven the 195 miles each way instead.
But as a male with broad shoulders, if somebody is in the middle seat I always try to lean into the aisle a bit so that the person has a chance at being at least not miserable.