For some reason, I had never noticed this part before until I saw it in the theater yesterday.
They had some trivia questions before the film started, one was "how many characters did Jim Henson voice in The Muppet Movie". I actually felt stuck counting in my head how many of them spoke, I think the "correct" answer was 7 though only Kermit, Rowlf, Dr. Teeth, and The Swedish Chef have dialogue. Though while watching I remembered that Henson dubbed some dialogue for one of Doc Hopper's henchmen who fights Miss Piggy, and somebody on Facebook said that one of the chickens Sweetums slaps during the credits makes a sound that sounds like a Henson voice (easier to hear in the UK version). It listed what characters Henson performed, I didn't have much time to read but I noticed it listed Link, who doesn't have any dialogue (I'm guessing The newsman was listed despite basically the same deal, of course there's also a lot of Henson characters at the very end). I do wonder if maybe I misread The Muppet Show for The Muppet Movie. And of course the question was who did he voice - the performers would say they performed, not voiced.