Two different versions of the ending were shot. In the broadcast version, Carol says that a new episode of the show will be on Friday night following "Donny and Marie," which segues into the closing rendition of "United We Stand." The alternate version is practically the same, but she omits the information about the upcoming airing.
Christopher Knight was supposed to perform "Sing" as a solo, but the challenge proved too daunting for the self-proclaimed tone-deaf young actor. They ultimately brought in a Krofft puppet named Collette (voiced by Florence Henderson) to sing the lead, with Knight singing back-up.
Milton Berle was notorious for taking over the productions in which he appeared and bossing everyone around, so they wrote it into the storyline.
Milton Berle was renowned for being extraordinarily well-endowed. One day, he popped his head into the writer's room and asked where the bathroom was. After he walked away, there was a moment of silence and then the writers stood up as if they were going to follow him to sneak a peek, which broke them all into hysterical laughter. The most brazen of the bunch was Bruce Vilanch, who outright asked to see it, though Berle declined his request.