I think it's fake. The other guy probably put a bit of lighter fluid on him so that he would light up quickly. Fart flame don't light people up that quickly.
I have lighten my fart once! It was hilariously! I couldn't stop the laugh for too long! Planning to do again, but problem is laughing is too much for me! If you want try for yourself, the stronger the smell your fart is, the stronger the flame it is gonna to happen!
The reason for fart to light up is that your fart actually contains methane, same gas for natural gas at your home!
Its quite possible! Why these guys looks like they have prepared, and was able to act fast? If they weren't prepared, the guy who farted will probably hesitate and trying to figure out how to save his friend, rather responding so fast.
I think it's fake. The other guy probably put a bit of lighter fluid on him so that he would light up quickly. Fart flame don't light people up that quickly.