So my friends and I have been using this technique to approach groups of girls. Inspired by the show Workaholics (can't really find a link to it), this is what you do:

Walk up to a group of girls and say something along the lines of 'hey, my friend thinks that he can make a smaller face than me, can you guys be the judge so we can finally settle this?'. So now, their usual response is that they're confused, but intrigued. The next step is to count down from 3 to your buddy, and at simultaneously pull your lips up toward your nose and close your eyes to shrink your face. Honestly, they love it. They will sometimes even ask you to demonstrate a second time. After the victor has been decided, tell them to compete! (HB's look so damn cute doing it too haha)

This has worked 6/6 times for me, and has led to decent conversations and #-closes. Go out and try it!

EDIT: Found a clip from the show! http://i.imgur.com/PIbke.gif