This phrase is a derogatory saying that usually denounces someone's style in something. "X" is usually replaced with a time period whom the person's style reflects. "Y" is replaced with the item being made fun of or denounced.
Another permutation of this saying is more common on imageboards, messageboards, and forums. china called...
Examples of X Called, they want their Y Back...
Hey, Justin Bieber called, he wants his singing skills back.
Hey, the 1970s called, they want their clothing back
Hey, Elvis called, he wants his hair back
"Back of the Y is without a doubt the greatest thing to grace our television screens in many years. If youre looking for a half hour of full kicking, mind blowing, no budget, stunt laden wanking jokes then this is for you. While everyone seems to be talking about the American series 'Jackass' at the moment, its good to see that our own home grown Kiwi dumbasses Matt Heath and Chris Stapp have once again risen to the challange and made a show so stupid and funny that it makes any jackass look lameass."
"Listen im gonna say this once! DRUGS, are for GROWN UPS! GO TO BED!"