It would make sense for the Muppets to have popular stars like Zack Efron on a show, but also other more enduring celebrities.
At any rate, I honestly don't know most of the stars from the first season of the Muppet Show (as well as the second). I know some of them, but the point is, the Muppets kept me interested.
Actually, I think an interseting idea for a Muppet Show could be to have adverage people off the streets interacting with the Muppets... Somewhat like the Sesame Street characters interacting with kids, but a whole show about it, you know? Yes, there would also be big named celebrities involved, but I personally think people could really relate to seeing adverage, unknown people on the Muppet Show!
Imagine a skit that is set up like a talk show and Kermit, the host, introduces someone with an interesting talent and then other Muppets get involved and perhaps Statler and Waldorf would heckle from their theater box. The whole skit would only take two minutes, but it would be a lot of fun for everyone, I think.
Maybe this idea sounds better in my head than it really is, but I like it.
Oh, and come celebs I would like to see with the Muppets include:
Oprah (now that would be a sight to see)
Anne Hathaway
Ellen DeGeneres
Jim Carrey
Robin Williams
Johnny Depp