In Mega Man X, it is possible to learn the "Hadoken", Ryu's signature move from the Street Fighter series. After beating the game, obtain every Sub Tank, Life Up and Armor Parts. Then play through Armored Armadillo's stage until the last rolling platform. As the platform bursts out of the tunnel and through the sky, dash-jump off of the platform and ascend the wall right on top of the gate to Armored Armadillo. There you will find Dr. Light wearing a Karate uniform. He teaches X the technique.