Complex sentence: The last few sketches involved the Muppet characters trying to negotiate with various cast members and guest stars for the sketch's continuance, but to no avail; the Land of Gorch characters were not seen after the first season.
Split into simpler sentences: The last few sketches involved the Muppet characters trying to negotiate (unsuccessfully) for the sketch's continuance. The Land of Gorch characters were not seen after the first season.