Spike Ball is an ability learned by Bowser in the game Mario & Luigi: Bowser's Inside Story. The ability is learned when Mario and Luigi cure Bowser of his back pain by drilling into a strange spot at the Lumbar Nook. When they finish the process, Bowser's back loosens; he becomes more flexible and can access the Spike Ball ability. This ability allows Bowser to roll up into his shell, become a ball and climb walls of soft dirt, smash through certain objects, get shot through a spring and activate treadmills in the overworld.
When Bowser learns the Spike Ball, he suggests that he could never roll up into a ball before. However, the Special Attack Shy Guy Squad has Bowser roll up into a ball. These Shy Guys are rescued long before Bowser learns the Spike Ball.
A slightly similar ability was utilized in Super Mario Galaxy during the last fight against Bowser. It could be countered by a Stretch Plant.