to 35 per season—and to create a spinoff series with the Sesame Street Muppets, and a new educational series. At its 50th anniversary in 2019, Sesame Street had produced over 4,500 episodes, two feature-length movies (Follow That Bird in 1985 and The Adventures of Elmo in Grouchland in 1999), 35 TV specials, 200 home videos, and 180 albums. Its YouTube channel has almost five million subscribers. It was announced in October 2019 that first-run episodes will move to HBO Max beginning with the show's 51st season in 2020. Format From its first episode, Sesame Street's format has utilized "a strong visual style, fast-moving action, humor, and music," as well as animation and live-action short films. When it premiered, most researchers believed that young children did not have long attention spans, and the show's producers were concerned that an hour-long show would not hold their attention. At first, its "street scenes"—the action recorded on its set—consisted of character-driven interactions. Rather than ongoing stories, they were written as individual, curriculum-based segments interrupted by "inserts" of puppet sketches, short films and animations. This structure allowed producers to use a mixture of styles and characters, and to vary its pace, presumably keeping it interesting to young viewers. However, by season 20, research showed that children were able to follow a story—and the street scenes, while still interspersed with other segments, became evolving storylines. On recommendations by child psychologists, the producers initially decided that the show's human actors and Muppets would not interact because they were concerned it would confuse young children. When CTW tested the new show, they found that children paid attention during the Muppet segments, and that their interest was lost during the "Street" segments. They requested that Henson and his team create Muppets such as Big Bird and Oscar the Grouch to interact with the human actors, and the Street segments were re-shot. Sesame Streets format remained intact until the 2000s, when the changing audience required that producers move to a more narrative format. In 1998, the popular "Elmo's World," a 15-minute-long segment hosted by the Muppet Elmo, was created. Starting in 2014, during the show's 45th season, the producers introduced a half-hour version of the program. The new version, which originally complemented the full-hour series, was broadcast weekday afternoons and streamed on the Internet. In 2017, in response to the changing viewing habits of toddlers, the show's producers decreased the