“Sesame Street” was originally intended to help prepare children from disadvantaged backgrounds for school, and the shows were carefully designed to keep their attention while helping them learn, as in this clip where Oscar unwittingly helps Nicole Kidman explain the meaning of “stubborn.”

Researchers had advised against mixing the Muppets and human characters, because it could be confusing. But after the street scenes with only human characters fell flat with test audiences, the creator of the Muppets, Jim Henson, decided to add Big Bird and Oscar, the author Michael Davis wrote in his book “Street Gang: The Complete History of Sesame Street.”

In a 2010 interview, Charlotte F. Cole, then a senior vice president for global education at Sesame Workshop, which runs the show, explained that Oscar was intended to “help children understand different perspectives.”

“He likes noise, where other people would like quiet,” she said. “He likes trash. By having this character, it was a vehicle for children to see that other people look at different situations in different ways.”

Dr. Paul Donahue, a child psychologist in Scarsdale, N.Y., said that Oscar personified the jumble of strong feelings that children experience and must learn to sort out.

“He allowed for ambivalence,” he said. “You could be a little cranky and irritable or grouchy and that didn’t mean that you were a bad person.”