Info Wanted: Help identifying a bit of behind-the-scenes film

I’ve located a bit of 16mm film - about 3mins all told - which features some behind-the-scenes shots from Dark Crystal, Empire Strikes Back and Return of the Jedi, intercut with clips from the finished films (plus a bit of The Great Muppet Caper for some reason) and a brief clip of Jim Henson talking.

It’s been suggested that this may be an excerpt from <span>Classic Creatures: Return of the Jedi, but not having seen this I can’t confirm.  Does the above sound at all familiar to anyone?  If it’s taken from a documentary then it’s probably of little interest, but if it’s unique then I shall see about getting it put onto video.</span>

Thanks!

Please explain any of the clips in greater detail. 

Classic Creatures is on youtube in various versions: http://www.youtube.com/watch?v=k6viLdh5nXQ

That's it - thankyou very much!  The film I have is from http://www.youtube.com/watch?v=MWYT3UReBiU&feature=relmfu , starts about 50 seconds into the clip and runs for 3 minutes.