GolfScript, <s>162</s> <s>154</s> <s>152</s> 144 bytes
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    "I'm ":i"Slim ":|"Shady":y". Yes, "i"the real ":!y".
    All you other "|y"s are just imitating.
    So, won't "!|y" p""lease stand up":l"?
    P"l". P"l"."

[Test online](http://golfscript.apphb.com/?c=IkknbSAiOmkiU2xpbSAiOnwiU2hhZHkiOnkiLiBZZXMsICJpInRoZSByZWFsICI6IXkiLgpBbGwgeW91IG90aGVyICJ8eSJzIGFyZSBqdXN0IGltaXRhdGluZy4KU28sIHdvbid0ICIhfHkiIHAiImxlYXNlIHN0YW5kIHVwIjpsIj8KUCJsIi4gUCJsIi4i)