Whenever we have made ressies for Hoop Dee Doo or any of the others, we have always had to go to Guest Services at our resort beforehand to "check in" for the dinner show.
They gave us a voucher like ticket (couldn't be folded or tear the perforration) that needed to be presented at the Hoop Dee Doo, etc. Not sure if they are still doing this. Our last time doing a dinner show was in 2006.