<P> During the production of Sesame Street's first season, producers created five one - hour episodes to test the show's appeal to children and examine their comprehension of the material . Not intended for broadcast, they were presented to preschoolers in 60 homes throughout Philadelphia and in day care centers in New York City in July 1969 . The results were "generally very positive"; children learned from the shows, their appeal was high, and children's attention was sustained over the full hour . However, the researchers found that although children's attention was high during the Muppet segments, their interest wavered during the "Street" segments, when no Muppets were on screen . This was because the producers had followed the advice of child psychologists who were concerned that children would be confused if human actors and Muppets were shown together . As a result of this decision, the appeal of the test episodes was lower than the target . </P> <P> The Street scenes were "the glue" that "pulled the show together", so producers knew they needed to make significant changes . The producers decided to reject the advisers' advice and reshot the Street segments; Henson and his coworkers created Muppets that could interact with the human actors . These test episodes were directly responsible for what writer Malcolm Gladwell called "the essence of Sesame Street--the artful blend of fluffy monsters and earnest adults". Since 2001, the full rights for the Sesame Street Muppets have been owned by Sesame Workshop, as the CTW was renamed in 2000 . </P> <P> The first Muppet to appear on the show was Big Bird, an 8 - foot - tall yellow bird believed by writer Shalom M. Fisch and Dr. Lewis Bernstein to be a canary, who resides in a large nest alongside the "123 Sesame Street" building and represents the 6 - year - old child with his tendency to question everything . Also living outside of the building is Oscar the Grouch, a trash can - dwelling creature belonging to his own unique species, who is portrayed as a habitual pessimist and was designed to give children "permission to feel grouchy--and to demonstrate differing opinions". Oscar and Big Bird were specifically created for the reshooting of the "Street" scenes with the idea that they would be able to interact with the human characters . Big Bird's best friend is Aloysius Snuffleupagus (better known as "Snuffy"), who was portrayed as the bird's imaginary friend until revealed to the human cast in 1985 . For his part, Oscar has several friends of his own despite his pessimism; these include the Grouch's pet worm, Slimey, and his girlfriend Grundgetta . Two other Muppets who have appeared on the show since its beginning are Ernie and Bert, a pair of best friends with contrasting personalities; Ernie is portrayed as a free - spirited trickster who loves his rubber duck, while Bert is the world - weary foil to his friend's naïve trouble - making, and shows himself to be obsessed with things like pigeons and paper clips . </P> <P> The Three Bears from the story of Goldilocks appear in Muppet form on Sesame Street . Also appearing on the show are an unidentified species of furry characters referred to as "monsters". Among these are Cookie Monster, a blue monster who is addicted to the baked goods for which he is named but ironically also likes healthy foods; Telly Monster, a purple worrywart who overthinks everything, was described by writer David Borgenicht as "neurotic", and was originally portrayed as a television addict; Zoe, a yellow - orange female monster who is "simultaneously dainty and strong, practical and impulsive" and loves to dance ballet; and Rosita, a bilingual turquoise monster (also female) who speaks both English and Spanish . Grover, a blue monster described by Borgenicht as "self - confident, furry, cute, capable, and intelligent", has a superhero alter - ego named "Super Grover", who is more well - meaning than helpful . In addition to Ernie and Bert, recognizable humanoid Muppets appearing on the show also include Count von Count, a number - obsessed vampire based on Bela Lugosi's interpretation of Count Dracula; and Prairie Dawn, a methodic and driven young girl who loves to write and direct pageants featuring her friends . </P>

Who was the first character on sesame street