[Cry Me A River]

"Great Scott" is a double reference.

Heroes is a show about super-heroes. Hiro is a super-hero. A time travelling super-hero. Hiro is a comic fan, he was using it as a Superman reference. The show is also using it as a Back To The Future reference. It's actually pretty clever.

It's FAR more likely Hiro read Superman comics in the original English than watched Back To The Future in the original English. However, it's certainly possible he's aware of both usages.

In the online comic adaptation of Heroes, Hiro owns a copy of Action Comics #1.