Why not credit Kenny Baker as R2-D2 on The Muppet Show?

Question

Given the release of The Force Awakens and my subsequent introduction to the Star Wars universe, it seemed appropriate to rewatch Episode 4.17 of The Muppet Show, guest starring "The Stars of Star Wars": Luke Skywalker, C-3PO, R2-D2, and Chewbacca. The credits are given as follows (including the lack of droid name hyphenation; that's just how they wrote it).

Special Guest Star

MARK HAMILL

with Guest Stars

ANTHONY DANIELS as C3PO

PETER MAYHEW as Chewbacca

R2D2 as Himself

R2 most definitely "speaks" throughout the episode, and IMDb says that Kenny Baker is the man responsible for those bleeps and bloops, so why isn't he named in the credits?

Answer 1

According to this interview on the Starwarz.com website, Kenny Baker wasn't involved in the Muppet Specials. In those occasions when R2-D2 was required to make a celebrity appearance, they would use the remote-controlled (three-legged) prop that was used when R2-D2 wasn't required to walk upright.

Q. "Were you ever in the R2 suit in anything outside the films like specials, TV appearances, premieres, etc.?"

K.B. "No. On the few times that there was a Star Wars special they would use the three legged R2, like on the Muppet Show. Anthony and Mark did a few shows though."

Answer 2

In the movies, the beeps and boops aren't made by Kenny. They were created by Star Wars sound designer, Ben Burtt, and weren't added to the film until well after they were done filming. Kenny Baker was actually the physical actor performing the movements for R2-D2. He would be inside the shell and could turn his head, extend devices, move, turn, etc.

In The Muppet Show, no one was actually in the R2-D2 contraption, nor creating new sounds. Everything R2 "says" is just reused sounds from the films, and all his movements are simple remote control actions. Because of this, R2-D2 is fairly accurately credited as playing himself, though his performance is the end product of a lot of designers, engineers, technicians, artists, and more. It wouldn't be reasonable to credit everyone that went into that process, anymore than it would be reasonable to credit the stage hands and set construction team and such for "playing" the role of "Curtain".