Why do the English make fun of Wales & the Welsh in particular?

Im speaking in films and on the tele. If "wales" is mentioned the actors say "oh is it as bad as that?" or "oh no, not wales". Or Welsh being used in the derogatory.

I hear it used about every other area like Ireland & the Irish and every other place, but why the direct special distaste for the Welsh & Wales?
So what I'm getting from the responses so far is that the Welsh are the least exposed to English domination throughout history? At least lingually and probably culturally? So that distinction has earned them exaggerated negative attributes according to the English?

So what is some typical negative stereotypes of the Welsh?
I mean what *are* ....
I'll give the best answer to "Cymro bach" although I think jealousy is not the term you're looking for, its more like "Resentment" for all the reasons you described.

Does anyone know of any films I can get in the US with people speaking Welsh. Or any websites that has sound files (preferably with full sentences spoken). Also, can someone recommend a website or audiobook that teaches pronunciation with soundfiles so I can hear it. Thanks in advance.