Oh, the irony. "Your retarded" is incorrect. It should be "You're retarded". Saying "your retarded" is just making yourself retarded by not knowing the correct grammar.
Billy Bob: your retarded
Sally: Look who's talking. Get some grammar lessons, retard.
a joke which reveals the veritable retards around you. lacking recognition of the irony, the bona fide retard will correct your grammar, thereby revealing their qualifications for the special olympics.
An ironic misuse of the word your. As a last ditch effort to conceal one's own mental failings, often people will claim it was a joke; however, only people more retarded than the initial tard will believe they were actually joking, and also that typing "your retarded" constitutes as a joke.
Jim: No, you mean you're retarded as in you are retarded.
Dick: No bro, I was being ironic, you know? Your retarded.
Jim: Funny... don't have children.
An extremely lame joke that is 1% irony and 99% gay.
"Why does your shirt say, 'Your retarded'?"
"OmGzzz you d0nt get it???"
"That joke sucks"