The production company behind Sesame Street is asking political campaigns to refrain from using their characters in campaign ads — including an Obama campaign ad that uses Big Bird.

"Sesame Workshop is a nonpartisan, nonprofit organization and we do not endorse candidates or participate in political campaigns. We have approved no campaign ads, and as is our general practice, have requested that the ad be taken down," the company said in a Tuesday statement.

The Obama campaign released an ad early Tuesday that hit Mitt Romney on his proposal to defund PBS. The ad features Big Bird, who has become a symbol of the debate over funding public broadcasting.

Since Romney's in last week's debate, Sesame Street — and Big Bird in particular — has emerged as a campaign line, with Obama repeatedly hammering Romney on the issue.