Tails grabbed his shrink ray and shrink the red echidna down to a small size and placed him directly under his feet which he then proceeds to entrap him inside of his shoes as punishment.
Tails has trapped Knuckles deep within his shoes as punishment, forced to put up with his big feet compressing on him and the humid atmosphere for a few hours. Knuckles is durable so he can tough it out until then. Unfortunately, Tails has captured Sonic in the same way from an earlier time. Sonic allegedly knocked over one of Tail's newer inventions and went from there to punish him.
