Well minor muppetz, I looked at imdb.com and according to them Roosevelt Franklin skits were from 1969-1972, Professor Hastings was from 1970 only (no wonder there weren't too many!), Herbert Birdsfoot skits were from 1970-1973, Little Bird was from 1970-1986 and 1990 (I would have thought that Little Bird was ended in the 70's but I guess Fran Brill, at least occasionally, continued to do more LB skits) and Harvey Kneeslapper was from 1970 to 197? . So some time in the 70's was the final HK skit. I would guess late 70's since they made quite a bit.