What Is The Event From Sonic 2's Manual That Sonic Adventure 1 References?

what is the event from sonic 2's manual that sonic adventure 1 references?

Tails’ flashback:

From the manual:

“Miles Prower” is a small fox. Miles has two tails. That is why the animals of the island call him “Tails.”He was often bullied because of his two tails. But after seeing Sonic, who came to this island, Miles changed. He made up his mind.“I want to become cool, too!” he said. And after that, Miles began following Sonic around throughout the day.

The part about him being bullied is also brought up in his introduction line for prerelease materials: