"Sesame Street" returned to cyberspace on Monday after its YouTube channel was targeted by unknown hackers who replaced Ernie, Abby, Big Bird and the Cookie Monster with hardcore porn.

YouTube, owned by , pulled the channel down Sunday when its wholesome children's fare was replaced with adult videos and the headline: "Sesame Street New Content Special for Kids! Brought to you by Mr EdWxwx."

"We apologize for any inconvenience our audience may have experienced yesterday on our Sesame Street channel," said a statement on www.youtube.com/sesamestreet after it came back online.

"Our channel was temporarily compromised, but we have since restored our original line-up of the best classic Sesame Street video clips," starting with an animated video about standing up to bullying.

A YouTube spokeswoman told AFP: "YouTube's community guidelines prohibit graphic content. As always, we remove inappropriate material as soon as we are made aware of it."

Seen on television around the world, "Sesame Street" on YouTube had nearly half a million subscribers.

The identity of the was unknown, but on his gaming-oriented YouTube channel, Mr EdWxwx was emphatic, if in need of some spelling lessons: "I did not hack Sesame Street I am an honsest youtuber I work hard to make quality gameplay videos and most important I respect the community guidelines."