Just trying to add some variety the Mario Kart info, there will be plenty more Mario Kart info to come, don't' worry ;) This is to show you how to throw your bowling backwards and get a reaction from the crowd.
This especially fun when you have some friends over to show off a bit, you can roll your bowl backwards and make all the miis in the crowd jump, kind of fun. Below is a YouTube video of it
Basically you just let go of the trigger on your back swing and it should work for you, I was able to do it on my first try. Plus, it let's you re-throw, so you can show off during a game and it will not effect your scoring!