Dr. Frankenstein’s creature begins to win audience after walking forward and then back. Inga is very happy to see the performance is going well. The doctor addresses the crowd and tells them he is going to impress them even more by presenting a sophisticated, cultured, man about town. The lights go down and then, in the blackout, we hear, “Hit it!” The lights come up and reveal both Dr. Frankenstein and his creature in tuxedos. Music for Puttin on the Ritz begins and so, too, does the song and dance number.
There is an interesting backstory to this entire scene. Apparently, Mel Brooks did not think having the song and dance number was funny. He actually thought they should drop the bit and save the production costs. Gene was upset and began to argue his case. The story goes, he argued to the point of tears, getting red in the face. After 25 minutes, Brooks relented. He said if Gene was that adamant about it, it must be okay to leave in the film.