After four decades, "Sesame Street" and the Muppets are inextricably linked.

And yet when Jim Henson brought the Muppets on board, it was a big departure.

"My father was kind of surprised to be pulled into educational programming because, as a puppeteer, he often stayed far away from the kind of birthday party, little-kids' entertainment puppetry," said Lisa Henson, chief executive officer of The Jim Henson Co.

"But, of course, it was incredibly rewarding for him and for all of his collaborators. And I think most people would say that was one of the greatest high points of the Muppets, that they could be there from the beginning of 'Sesame Street.' "

And it has indeed been 40 years. The first episode aired on Nov. 10, 1969.

"When I travel around the country and give speeches, I mention the 40th anniversary of 'Sesame Street' and some people smile," said PBS president Paula Kerger. "And some people look obviously stricken, because they remember when 'Sesame Street' came on the air.

"I think that what 'Sesame Street' has done so extraordinarily well over its history is really set the standard for the best of children's programming."

When the show premiered, most homes had access to maybe four or five channels. Few people had cable hookups, and those who did used them to get better reception of broadcast signals. (The were no cable networks until 1972.)

Things like VCRs, DVRs and the Internet were almost the stuff of science fiction.

And the idea of educational programming for preschoolers was revolutionary.

"We were literally the only game in town," said Miranda Barry, executive vice president of content for Sesame Workshop. "I think there are now 47 preschool shows on television in various places."

And, while there are plenty of good programs out there — including the PBS kids lineup — none of them have the cachet or impact of the "Sesame Street." And not just in this country.

"We're proud to say that ... we have become the longest street in the world," Barry said. " 'Sesame Street' is seen in over 140 countries, and we have become the largest informal educator of children the world over."

The curriculum of "Sesame Street" hasn't changed all that much since 1969. Rosemarie Truglio, vice president of education and research for Sesame Workshop, pointed to "cornerstones" like literacy and mathematics.