Thinner or Paint Thinner is green paint which does not restore an object. If anything is thinned, the thing will be erased.
Mickey is painting Cartoon Wasteland and spilt some Thinner and he created the Shadow Blot. Soon, the Blot drags Mickey to Wasteland and the Blot created Blotlings.
To use Thinner, you can use the Z Button. Using Thinner summons Turps to the Guardian Meter.