From the Super Mario Wiki
Fattingtons are morbidly obese enemies resembling ice cream that Wario comes across in Wario World. They appear in the Shivering Mountains. Due to their round body, Wario's punches have no effect on them; punching them will cause Wario to bounce back. To defeat them, the best strategy is to grab a Column, Sculpture or another nearby enemy and throw it at the Fattington. Wario can then pick up the Fattington and use a Piledriver, Wild Swing-Ding, or Power Throw to defeat it.