The image of the unlikely duo -- the "Sesame Street" character and the suspected mastermind behind the September 11 hijack attacks in the United States -- has been splashed across spoof Internet sites over the past month.

Mysteriously, the image made the jump from the virtual world to the real one, appearing on bin Laden placards at anti-American Muslim rallies in Bangladesh over the past week.

The posters, which show a tiny Bert tucked between two images of bin Laden, were clutched by seemingly unsuspecting demonstrators at rallies on October 5 and 9.

The banana-shaped Muppet is easy to miss at first glance.

Photos of the protest placards have been posted on scores of humor and news Websites after circulating around the globe via e-mail.

Astonished Internet users first noticed the appearance of Bert on Wednesday morning. By Thursday, it had become a raging debate on the Internet.

"Bert working with bin Laden?" reads a headline on Swedish Website www.lindqvist.com. A debate follows on the site as conspiracy theorists try to figure out the mystery of how the spoof photo made it onto the streets of Bangladesh.

Sesame Workshop, the non-profit company based in New York that oversees licensing of "Sesame Street" products, said in a statement it was exploring all legal options to stop unauthorized use of its property.

"We're outraged that our characters would be used in this unfortunate and distasteful manner. This is not at all humorous,"

"HONESTLY FREAKED OUT!"

Part of the mystery can be traced to California.

A San Francisco artist, Dino Ignacio, in 1998 started a conspiratorial spoof site called "Bert is Evil," in which Bert is inserted into famous historical photos.

He has appeared alongside Adolph Hitler and among a crowd in Dallas as John F. Kennedy's motorcade passes.

Ignacio put a statement on his site, www.fractalcow.com, on Wednesday denying he was the creator of the Bert and bin Laden image.

"I just wanted to say I had nothing do to with this!"

"This image has been e-mailed to me countless times since September 11. Yesterday a lot of you alerted me to a picture of a Taliban propaganda poster with Bert!"

"Reality is imitating the Web!" the statement continues. "I am honestly freaked out!"

The Bert-bin Laden poster contains a montage of bin Laden photos. One shows him holding a microphone and another wearing military fatigues sitting beside a propped-up Kalashnikov rifle.

Bert, wearing a menacing open-mouthed expression, appears between two of the images.

The posters were photographed by news organizations including Reuters, and distributed to newspapers and news sites around the world.