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Mr. Stringo is Baby Bear's lucky piece of string. It plays a major part in a 1998 episode of Sesame Street, where Baby Bear plans on using it as part of his collage, but is then stolen. He and Gabi look all over the street for it, until Big Bird shows them a bird friend of his has used to repair her nest for her two babies. In return, the bird gives Baby Bear a feather for his picture.
In a song Baby Bear sings during the episode, he says he'd use Mr. Stringo as a bookmark, a false mustache, keeping his mitten to his coat, playing with a kitten, eyes for a hand puppet and for tying around his finger.