GolfScript, 162 bytes
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<!-- language: lang-c++ -->

    "I'm ":i"Slim ":s"Shady":y". ""Yes, "i"the real ":r y".\nAll you other "s y"s are just imitating.\nSo, won't "r s y" p""lease ":l"stand up":u"?"n"P"l u". P"l u"."

[Test online](http://golfscript.apphb.com/?c=IkknbSAiOmkiU2xpbSAiOnMiU2hhZHkiOnkiLiAiIlllcywgImkidGhlIHJlYWwgIjpyIHkiLlxuQWxsIHlvdSBvdGhlciAicyB5InMgYXJlIGp1c3QgaW1pdGF0aW5nLlxuU28sIHdvbid0ICJyIHMgeSIgcCIibGVhc2UgIjpsInN0YW5kIHVwIjp1Ij8ibiJQImwgdSIuIFAibCB1Ii4i)