The channel, which hosted several dozen clips from the popular PBS children's program, was taken offline after it was hacked by a user calling himself "MrEdXwx." Clips from the show were removed and adult videos were posted in its place.
Internet screen grabs provided by ShortFormBlog.com show the banner on Sesame Street's YouTube channel was replaced with a graphic that read "It's where porn lives" along with a video description that reads "Who doesn't love porn kids?"
Several adult videos, one of which was eight minutes in length, were later uploaded to the channel. Characters from the Sesame Street program did not appear in any of the videos.
The channel was eventually closed down by YouTube due to "repeated or severe violations of our Community Guidelines," a note read Sunday.
YouTube later changed the message to read "This channel is not available." YouTube's terms of service says its users aren't allowed to upload pornographic videos.
Sesame Street's YouTube channel had over 140,000 subscribers as of Sunday. The channel gained notoriety last year when a published video showed a scantily-clad Katy Perry singing a rendition of her song "Hot 'n Cold" with the popular Muppet Elmo. The musical number never aired on the television program.
PBS and Google, the parent company of YouTube, have not yet commented on Sunday's incident.