AmericanItGirl- It changed because the original cast all retired, they fiddled with what to do with the GH for some time before bringing in the Billies.
In the old days, my family (especially my Grandmother), would race us all back to the GC to get our day's reservation so we could see the show. If you didn't get a reservation, you had to wait in the standby line and HOPE you got in. It was so popular all the shows would be packed!
One of my favorite memories was getting brought up in the show (they always picked one kid per show), and after wards they gave me one of the huge Lollapalooza lollipops, my dog ate it and I was very sad hahaha! I got picked twice which made my sister mad because she never got chosen (hahah I did that to her on the Who wants to be a Millionare game at DCA too!

).