Collect 5 stars in order to charge your special attack, press B to use it.
Skipper pulls out a megaphone and shouts orders which create a shockwave that makes your opponents spin. You can manually "fire" the shockwaves. It's best to do so when you are driving behind the pack, in an alternate way you could always hit the brakes and let you opponents pass to give them what they deserve. You'll need to hit 3 different opponents to make the achievement pop.