Scummy Bears are usually covered in fluff/dust/dirt after having been dropped on the floor or left in a pocket for a few weeks/months etc
A Gummy Bear sweet that is found by surprise down the side of the sofa/under the bed etc generally inedible except to those strange few who claim the mould adds to the flavour...
Girl: Yeah, thanks... Hey! this is a scummy bear! it's covered in fluff and missing an ear!!
Boy: ...I found it on the floor
TV Advertisement: 'Scummy Bears! Now with 25% more fluff!'