From the Super Mario Wiki
Wrecking Balls are objects that appear in Yoshi Topsy-Turvy. They are silver balls attached to chains that appear to be mounted in mid-air. The length of their chains can vary, with some having three or four parts to the chain. When the player tilts their Game Boy Advance system, they can cause the Wrecking Ball to swing, where the sharper the tilt is, the higher the Wrecking Ball will swing. Doing this can allow the Wrecking Ball to destroy objects such as Stone Blocks. Wrecking Balls also appear in some bonus missions, where players must use them in order to hit cymbal notes a certain amount of times. Additionally, Yoshi can use Wrecking Balls as platforms.