I'm curious who performed Roosevelt Franklin's physical aspect. Matt Robinson performed his voice, and various quotes credit Jim Henson with the puppet, but I am wondering who actually did the muppet performance. Was it Henson himself, or someone else?
Right now we don't know, and quite probably it wasn't the same performer every time (although no doubt they tried for consistency when they could for major skits and things like the Elementary School, where his movements seem consistent). As noted on Roosevelt Franklin's Mother, Loretta Long recalls that Henson puppeteered Mom, so he wouldn't have been Roosevelt in that sketch (and given the small pool at that time, Frank Oz would be the most likely cohort in the early skits to play Roosevelt, but that's speculation; chances are other times it was Henson, who it is known puppeteered at times characters like Little Chrissy, but again, that's "chances"). It's a good question though, and if we find any behind the scenes photos or other evidence to help source, we'll post it to the article or here. Thanks for asking.