Elmo's Sing-Along Series are a series of videos hosted on the Sesame Street YouTube channel. The series launched in August 2017 and features new videos starring Elmo, Abby Cadabby and Rosita, as well as sing-along versions of songs from the show.
One of the original videos, "Elmo Was His Name-O," was aired on the show in Episode 4803 (though edited).