I loved the two little Martian dudes and their "Yep yep yep yep" noises. They don't look like any other Muppet in use at the time, which is a part of their charm. They're almost kind of ethereal in their shapelessness. I love the way that their big chins snap upright when they're surprised or scared. Still too funny after all these years.
When I was looking for this sketch on YouTube, I was surprised at how many times these guys have been used. I remembered a few of them, but there were a lot that I was unaware of. It was a fun video search to do. The telephone bit is far away my favorite one, but I like this next one a lot too. It reminds me a little bit of the old fable about the blind men and the elephant, but with a fun twist. They can see the clock, but are trying to identify it using a book that is giving them ambiguous ideas. What fun.