During camera tests for The Muppet Movie (1979), Jim Henson, Frank Oz and a few of their associates got to improvising…
[NOTE: When I originally posted this, I said these were done during the filming of the movie. Corey Klemow and Andrew Smith both wrote to tell me no, these were tests made to see how the Muppets would look on the big screen. I have adjusted the text here accordingly. Thanks, guys!]