Mr. Cosby used a riff from “I Started Out as a Child,” his 1964 album, about playing street football as a youngster in Philadelphia. But he enhanced it: When he went out for a pass, he kept going and going and going, pursued by a young defender. He ran through the streets, a horse pasture, the tropics, a desert, someone’s golf game. Eventually Mr. Cosby jogged into the KNBC studio, where a live audience greeted him, and he appeared to have finally lost his pursuer. Turned out he hadn’t; when a pass was lobbed his way, the kid popped up out of nowhere and blocked it. It was a great extended sight gag, built from purely audio source material. Audio: An excerpt From Mr. Cosby’s “I Started Out as a Child.”

THE MAN WITH PERFECT PITCH At his best, Mr. Cosby has excelled at identifying his target audience and then serving it. When he wanted to make a family-friendly sitcom, he made the No. 1 show in the land. When he wanted a sitcom that pushed boundaries a bit, he made “The Bill Cosby Show” (1969-71), which is still admired for its subtle social commentary. And when he wanted to appeal to 3-year-olds, he was darned good at that too.

Mr. Cosby was one of the first celebrity guests on a fledgling PBS show called “Sesame Street.” On Nov. 9, 1970, in the show’s second season, he devoted 1 minute 34 seconds to the simplest of acts: reciting the alphabet. The segment uses a split screen to show two Bill Cosbys, identically dressed, alternating letters as they recite. The Cosby on the left, smiling shyly, is tentative, still learning. The one on the right is confident, a bit taciturn, nudging the other Cosby along with hints when he stumbles. To grown-up eyes, it may have seemed like just some guy rattling off the ABC’s. For the preschool crowd, it was a direct hit, giving young viewers someone to identify with no matter where they were in the alphabet-learning process. Video: Mr. Cosby recites the alphabet on “Sesame Street.”

COSBY THE CONTAGIOUS There may be no more beloved moment from “The Cosby Show” than a scene from an episode in Season 2 in which the Huxtable family lip-syncs Ray Charles’s version of “Night Time Is the Right Time.” But Charles had also turned up vicariously in another Cosby scene years earlier, one in which Mr. Cosby shows the skill that some stand-ups who try sitcoms don’t have: He makes the people around him funny. Video: The Huxtables perform Ray Charles.