Sonic accidentally drinks a potion that makes you become a child for an entire day (from when you drink it until the exact same time the next day), which was the potion Tails created. Well, Sonic, at 7:00 am, accidentally drinks it and after two minutes he becomes a child.

Tails enters the laboratory and doesn't find the potion.

Tails: "WHO DRINKED THE POTION?!"

A small blue hedgehog (It's Sonic) was hiding scared under Tails' desk.