But as far as I know, it is the first ever YouTube upload of the end credits to 20 and Still Counting, which was cut from the DVD and has been absent from all uploads I have seen, both before and after the DVD release (even uploads from the original NBC airing have removed it, or maybe too many people stopped recording before the credits).
But before the credits, at about the 56 minute mark, is a promo for The Jim Henson Hour with Jim Henson talking about the show. There was another promo in the middle that's a more generic promo, but this one, shown just before the credits, has Jim talking about the show and showing a variety of clips. As far as I can tell, this is not on YouTube on its own. It is a better promo than the other one that aired during the commercial breaks.
I've heard that 20 and Still Counting was originally supposed to be an episode of The Jim Henson Hour, and I wonder if I misunderstood that (maybe NBC agreed to some cross promotion and The Jim Henson Company produced an anniversary special). Jim's introduction is on a different set from the show and he's joined by Kermit instead of the lion. I wonder if this promo for The Jim Henson Hour is similar to the usual tags. I feel like it's a little longer, but I also know that most of the NBC broadcasts had a promo for next week's show at the end of the last commercial break. Perhaps it's the combined length of those promos and tags. The style is much different, this one showcasing clips from a variety of episodes (while the other promo is exclusive to the first episode, but also doesn't break down MuppeTelevision from The StoryTeller like the other promos do). It would have been neat if Jim Henson hosted promos for each individual episode like this.
I had started asking myself "did the first ad I saw air during the commercial breaks for Project: ALF?", then searched "Project: Alf commercial breaks", and found it! I guess it makes sense that a promo for a Muppets series would air during the broadcast of a puppet movie.
I feel like very few Muppets Tonight promos that aired on ABC (whether with or without exclusive footage) is online.
I had created a page for Muppets Tonight promos with info on that and another one with the same set (featuring an Elvis Muppet), as well as one with Bob Saget and Fozzie Bear, which nobody on the wiki had or made screengrabs from. Recently this has been discussed and those promos were taken off the wiki for the time being. Considering that, I am proud that I, the one who remembered them and put the info in the first place, was able to find one of them (now to find the others!). Somebody on the wiki also found a newsgroup post from 1996 where somebody said they just saw a promo with Bob Saget and Miss Piggy (as they are both Frank Oz characters, they likely did both at the same time).