There is a guy I know from school/playing football, Danny Bell, had a terrible stammer and used to get a fair bit of playground stick for it. Now he's on BBC Wilts every now and again doing film reviews, he joined the McGuire speech program and although there are a couple of times he pauses a bit, he's like a different person vocally.
The 'r' thing. My 4-year old son is similar, I don't think its too uncommon a young age. He also used to stammer but seems to have grown out of it. Thinking back my eldest had an 'R' problem, but that went away too.
But the point of the post - the name for being unable to pronounce R's. Rhotacism. Sick scientific world sense of humour.
Nae cunt kens whit ahm saying.
I ken. Lookin foward to the fitba with the wee bairn later.
I read Porno (Irvine Welsh's Trainspotting sequel) and the Scottish Edinburgh dialogue was written like that. Took quite a bit to get used to!