From the Super Mario Wiki
Graffiti Swing is Bowser Jr.'s Star Swing in Mario Super Sluggers. When used, Bowser Jr. will twirl his paintbrush in his fingers and then streak paint all around him, creating the effect. The ball will pop up, like the swings of Princess Daisy and Wario. However, a fake ball will land first, splattering the landing spot with paint and stunning any fielders who go to catch it. The ball will land a few seconds later. Unlike Wario's swing, fielders will go towards the ball by themselves, and they will get hit by the fake ball.
Although the move may appear flawless, levitating characters are completely immune to this move, which enables them to catch the ball and get Bowser Jr. out. The player can also buddy jump and catch the ball.