Stupid Guest Tricks

When they film the sing along videos in the parks, is it always a closed set?
or can you get a invite to the filmings? I found the GGG sing along on youtube and wonder how many takes it took to get a good version. I think I know how they hit thier cues on time, I bet they are all wearing mikes and headsets.
God, I would love to see the outtakes...
http://www.youtube.com/watch?v=eavo08IXduQ

We were at DCA when the cast from Shake It Up were in the park filming one of the "commercials' that talks about the Disney Channel show at DCA, they taped it in the morning before the park opened. We could see them taking photos when we were waiting by the Little Mermaid ride for rope drop.

I remember when they were shooting commercials for Knott's when I worked there. Kids wanted a part, but I kept telling them the casting was done months ago. Same thing when they opened the newest roller coaster, Pony Express, while I was there--just before I left.