The special is dated, especially with its reliance on early 3D CGI special effects, but it's delightful. The biggest revelation here is when Henson explains how the Muppets ride bicycles in The Muppet Movie and The Great Muppet Caper. This is one of the biggest mysteries of my childhood, and the explanation is in this video starting right at 33 minutes in. Warning: This might ruin the magic.
More details from Henson Rarities on this special:
Jim Henson takes viewers on a behind the scenes look at the making of The Jim Henson Hour and many other Henson productions. Back at the control room, the Muppets all freak out that their secrets are being revealed. NBC cancelled The Jim Henson Hour after nine episodes. This episode, filmed in 1989, first aired on American TV in 1992, as a stand-alone special on Nickelodeon. Jim shows how the room where he opens and closes each show is made. Jim does a demonstration of Steve Whitmire's character Waldo C. Graphic. Jim gives a tour of both the Muppet Workshop in New York and The Creature Shop in London. Rowlf leads a meeting of the O.M.D. (Organization of Muppet Dogs). Jim gives a behind the scenes tour of the taping and production of The Song of the Cloud Forest. Jim explains how Muppets ride bicycles. Jim finally introduces us to the main puppeteers for Muppet Central followed by footage on the making of "The Music Just Keeps On Rolling Along."