Phony Swing is Wario's Star Swing in Mario Super Sluggers. When used, Wario will pull out a large Bob-omb and hit it. Similar to Princess Daisy's Flower Swing, the ball will pop up, and slowly come back down. When the ball hits the ground, the Bob-omb will explode. Fielders will not approach the ball until after it lands, making this a good swing to use if the player is trying to score runs.
However, this move is not perfect, since if a fielder gets hit by the Bob-omb, another one will be free to catch the ball before it hits the ground. A fielder can also catch the ball by jumping and catching the Bob-omb itself. Both of these can get Wario out.