Over here in the US, all the original ITV logos have been replaced with new footage of Zoot blowing his horn (to the old soundtrack), checking his music notes, nodding because he LIKED the note, and then nodding to his fellow bandmembers offscreen! The background was all black so they wouldn't have to rebuild the stage set. I believe this change was done so that the ITV logo could be replaced with the Jim Henson Company's copyright information, since the rights had reverted back to them. (But ITV is mentioned elsewhere in the credits, so maybe I'm wrong. But I can't see any other reason for them to change it.)
I first saw the new ending when the show came to Nickelodeon in '94, though maybe someone else could let us know if this ending was also used when the show aired on TNT in '91.
Interestingly, Zoot is hatless in this clip, and it was placed over all episodes, even in ones where Zoot has his hat at the end. Even more strange, it was used on episodes where it made the ending confusing, such as the Dudley Moore episode where Animal runs out to the MAMMA Machine and does...something. Who knows? The soundtrack of Animal is still there, but Zoot is inexplicably playing his horn. Also in the Carol Burnett show, Carol is doing her broccoli monologue when Zoot's horn bellows and she says, "Oh, rats!" I'm guessing the camera stayed on her the whole time in the original, though here again it's replaced with Zoot.
When the show came to video and DVD, I noticed that they had a new Zoot clip! Zoot was now wearing his hat, he appeared to actually be in the orchestra pit, and he reacted with a stunned expression to the note he played. However, just because he's wearing a hat in this scene doesn't mean he's wearing it in the rest of the end credits, either. At first I was disgusted, but then I noticed that goes for the ORIGINAL filmed bits as well. It seems that they mixed scenes from different seasons in the end credits, so sometimes Zoot is wearing a hat or not. I can't tell you which seasons they were, though.
Sigh...I have no life.