Sesame Street has been on air since 1969 and was built on a genuinely radical idea: use the techniques of advertising to teach children letters and numbers. Short segments, catchy repetition, and characters designed to be memorable - the same tools that sold cereal, aimed at literacy instead.

It worked so well that it's one of the most studied educational programmes ever made, with decades of research showing measurable effects on school readiness. Very few television shows can claim that.

The Muppets are why it lasted. Jim Henson's designs are simple enough for a child to draw and expressive enough to carry real emotion, and each one covers a distinct developmental register - Big Bird's curiosity, Elmo's enthusiasm, Cookie Monster's total lack of impulse control, and Bert and Ernie's very patient friendship.

The show has also handled genuinely difficult subjects - death, illness, incarceration - with more care than most adult programming.

This collection covers Elmo, Big Bird and Ernie. Brought to you by the letter C.