A few that comes to mind for me.
Glen Close on "The Shiled" for one season was a great addition. I wish they would have been able to bring back the character in a different role, in the later seasons.
Comic-Book guy on the "Simpsons" I don't think he was around in the first few years of the show. I think he was a great addition to the cast.
Mr Furley on "Three's Company." I liked the Roper's but Furley was a upgrade because DOn Knotts is brilliant in everything he has done, just about.
Jason
Glen Close on "The Shiled" for one season was a great addition. I wish they would have been able to bring back the character in a different role, in the later seasons.
Comic-Book guy on the "Simpsons" I don't think he was around in the first few years of the show. I think he was a great addition to the cast.
Mr Furley on "Three's Company." I liked the Roper's but Furley was a upgrade because DOn Knotts is brilliant in everything he has done, just about.
Jason