Okay, this is a must. You are required by Federal Law (I think it got added sometime during the Carter years) to buy Season Two of The The Muppet Show, just out today on DVD.
Was this show The Greatest Thing In The History Of The World? Let's look at the evidence. On the second season alone, you had this hilarious appearance from Steve Martin:
John Cleese made an unforgettable appearance:
And--oh, look!--it's my favorite actor of all time Peter Sellers:
This season also had great appearances from Madeline Kahn, Cloris Leachman, Don Knotts and many more. Plus Teresa Brewer, singing "Music, Music, Music", and thus answering a question my siblings and I always had: What was that song our dad was always whistling?
Oh, also on this set, you'll get this little number. If it doesn't make you cry, then you're not worth knowing:
So summing up: Yes, The Muppet Show was The Greatest Thing Ever.