Except nacs are supposed to be whipped out so there isn't a trick called "nac whip", thus making this joke legitimate...

 Went and searched Nac Nac's, guess I'm wrong. I've always been told/know Nac Nacs to be the opposite of a Can Can, so instead of throwing a foot over the toptube and extending both legs, you throw both backwards and to the side, like a superman but with both kicked out to one side instead of over the middle of your bike.

 Those people are what you'd call... drunk