I agree Mickeyfanz. As a teacher I see many of the children that I teach, 2nd grade, who are not familiar with Dr. Suess characters because they are not being read to at home.
I think that children will be familiar with the characters that their parents expose them to.
My daughter who is 2 knows who Barney, teletubbies and clifford is, not because she's camped out in front of the television, but from seeing them in a moderate amount on TV, and from the Board books that she has.
Too be perfectly honest, she does not know any Suess characters and has only just know figured out who Mickey Mouse is because I planning this trip and see's him in my guide books, on my computer, etc..
So, in short I think kids are only familiar with characters that their parents may expose them to. Not only Disney, but Suess, Barney, etc..
zippehsmom