I doubt children are in danger of suddenly starting to talk like Baby Bear, unless that’s the only form of speech they hear. My kids all watched Sesame Street when they were little, and none of them started talking like Baby Bear, Elmo, or those Honker guys. As an example, I know quite a few children whose parents aren’t originally from the US. Mom or Dad may have an accent, but their US-born children do not. The reason behind Baby Bear’s speech impediment is probably just to go along with his babyish character. It isn’t uncommon for small children to speak the way Baby Bear does, but they typically outgrow it. Would you be concerned that a child watching Sesame Street might start to act like Oscar the Grouch? Develop an accent like the Count? I wish my kids were still interested in Sesame Street instead of Spongebob and Pokemon!