If I have a comedy show reservation for 5 people, would it be acceptable to arrive with 1 extra person, 6 total?

You need a reservation for the amount you bring. It will determine how they set up for the shows. I would call them or just make another reservation. They open the show to anyone outside to fill seats that don't get reserved.

You need the correct number, it books up fast

Call and find out, it's a full House and they even put multiple parties at the same table.