6. Justin Bieber

Rubie’s Costume Co. Child Justin Beiber Wig, $8
Blue Crown Midtown Slim Fit Mens Hoodie (Purple), $25
Supra Skytop Black/Grey/Purple-White, $100
Microphone, $3 

Justin Bieber is a pretty surefire hit. Just keep away from karaoke machines if you can't really sing, but you better work on your dance moves to keep up the illusion.