Bill Cosby (b. 1937) is a popular comedian who got his start making appearances on the likes of The Jack Paar Show. His career took a dramatic turn in the television series I Spy, and he reached superstardom in the 1980s with The Cosby Show.
Cosby has frequently appeared with the Muppets, particularly through Sesame Street, where he appeared in frequent inserts in 1970. Following the success of Sesame Street, in fact, Cosby appeared as a regular in the first season of The Electric Company, the Children's Television Workshop's follow-up series aimed at older children. Many of his segments on that series, such as twins (via split-screen) pairing off word sounds, were reminiscent of the Sesame Street skits. Cosby's other children's work included the animated series Fat Albert and recurring appearances on Captain Kangaroo, in separate "Picture Pages" segments.
In 1989, he served as host of the TV special Sesame Street: 20 and Still Counting; in one segment, in reference to Cosby's frequent billing in certain productions as "Dr. William H. Cosby, Jr., Ed.D.", Oscar the Grouch refers to him as "Ph.D. Face."
The following spring, in 1990, several Muppets from The Jim Henson Hour appeared on the Cosby Show episode "Cliff's Nightmare."
Most recently, in 2004, Cosby appeared in a "My Favorite Sesame Street Moments" segment.