"the royle family" joke

for anyone who doesnt know (e.g. anyone not from england, anyone who doesnt have a telly, etc) the royle family are a family in a tv show of the same name, its a fictional sitcom, and its not to be confused with the royal family, which is a real-life tragedy lol. i cant remember the wife's name (but i think shes played by caroline aherne ) but the husband is called jim royle and his famous catchphrase is, "my arse!"
it helps if u know a bit about the show before u read the joke.
anyway... it goes like this...
one day a burgular breaks into the royle family house and steals their telly. they love watching tv and they get a new tv, and decide that they need some sort of security cos they dont want to have their tv stolen again.
mrs royle decides they should have a guard dog so she goes to the pet shop and asks the owner for his best guard dog. he shows her a tiny pekignese dog and says thats his best guard dog. mrs royle says "that cant be a guard dog!"
the owner says "he is a guard dog. hes specially trained and he can do karate. if you tell him what to do, he'll do it."
so he gives a demonstration. he says to the dog, "karate my chair!" and the dog smashes his chair with his paws until its reduced to sawdust.
then he puts the dog on a table and says, "karate the table!" and the dog shreds the table with expert karate moves.
mrs royle is impressed by this and buys the dog, and takes him home.
she walks into the living room and jim royle says, "have u got a guard dog?" and she says yes and shows the little dog to him.
mr royle cant believe it. "that cant be a guard dog!"
mrs royle says, "that is our new guard dog. he can do karate!"
jim royle doesnt believe it, and of course he says, "karate my arse!"