Herbert Birdsfoot first appeared on the show in 1970 and was only there for a couple of years. He was originally made to replace Kermit. Kermit actually left Sesame Street during the second Season, and came back at the beggining of the third. A lot of people don't know that, but it's true. Herbert Birdsfoot stayed on during Kermit's first season back (Season 3) but he left either after that, or at the end of the 4th Season. I think he was originally supposed to be a more popular charachter, becuase he is included in many old Sesame Street recordings. Especially in group scenes with all the other charachters. Believe it or not, they actually reaired some of his old skits during the 80's and 90's on the show. So in a way he was there for a lot longer than he really was. The last time he was ever on the show was in a 30th Season episode in an old skit when Ernie throws a surprize Party for Bert. It's the same episode when it was Linda's Birthday and Snuffy goes into Oscar's Can. It's funny how even though he only lasted a few years, they continued to air his old skits for over 25 years. While charachters like Roosevelt Franklin, and Profesor Hastings, they pulled all the old skits with them when they no longer appeared in any new material.