Hahahaha, how can you not looove kpop idols? 
So the ones in this vid. is :

2PM, 2AM, Beast, MBLAQ, SHINee, Super Junior

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If you can't see who is who:

2PM, 2AM, Beast - Sign (Brown Eyed Girls)
0:32 Hwang Chansung of 2PM 0:37 Lee Junho of 2PM 0:48 Yoon Doojoon of Beast 1:16 Jo Kwon of 2AM

MBLAQ, SHINee, Super Junior - Muzik (4Minute)
2nd song = Muzik ( 4Minute ) 2:14 Shindong of Super Junior 2:23 Key of SHINee 2:33 Lee Joon of Mblaq 2:39 Mir of MBLAQ (in pigtails)

2PM, Beast - Mister (Kara)
3rd song = Mr. ( Kara ) pink pants = NichKhun of 2PM, blue pants = Kikwang of Beast, yellow pants = Jang Wooyoung of 2PM, red pants = Yoseob of Beast

SHINee, Super Junior - Gee (SNSD) 4:53 Taemin from SHINee 4:58 Sungmin from Super Junior 5:01 Heechul from Super Junior 5:56 Minho from SHINee 6:05 Leeteuk from Super Junior

2PM - Bo Peep Bo Peep (T-ara)
5th song = Bo Peep Bo Peep ( T-ARA ) blue sweater = Kim Junsu of 2PM red sweater = Nickhun of 2PM yellow sweater = wooyoung of 2PM gray sweater = jun ho of 2PM