I have seen in once. I was in a theatre with over 100 hundred fans. They were all dressed in very RHPS outfits and pulled all the jokes and sung and danced to all the songs. It was amazing. And we threw rice and played with latex gloves.

Audience: "Dude! Where's your neck?"
Narrator: "...lost in time..."
Audience: "WHERE'S YOUR smurfING NECK?!"
Narrator: "...lost in space..."

"ELBOW SEX! ELBOW SEX!"

Also, you've never seen a greater sight than 100 cross-dressing, scantily clad men and women performing the Time Warp. Holy mother of Awesome.