I wouldn't agree, Sylvester Stallone came on the show willing to act silly and couldn't carry a tune in a bucket, most of the singing scenes were cringe worthy. Not all guests have to sing like John Cleese but he pulled this off with skilled writing and performing. I think the trouble would be with finding a guest star is that the modern days there aren't many celebrities, actors and singers who have come from the variety circuit background, thats was what was great with the best guest stars from the classic Muppet Show. Being the guest star isn't the same as being the host of SNL you have to be able to tell jokes, sing, act and naturally interact with the Muppets. I don't want them to make a new Muppet Show for it to go down the Muppet Tonight route cutting almost all song numbers and just having sketches, the music was often some of the best parts of the original show.