Once, when Gai was still a young boy, he stole a green jumpsuit. He was then arrested by a Konoha policeman.

"Sorry, son," the policeman apologized. "I'll have to strip-search you."

"Lemme go!" Young Gai cried. "I'm scared!"

The policeman sighed. "It's Konoha policy. But, no hard feelings, right?"

Gai screamed and sobbed. "NOOOO! I'M BEING TRAUMATIZED!! NOW, I'LL GROW UP WEIRD AND SOCIALLY AWKWARD!"

The policeman ignored him, and began to strip-search Gai.

And thus, Adult Gai was born.