"Run" is the fifth episode in the fourth season of Smallville, and seventy-first episode overall. It aired on October 20, 2004. Smallville Wiki

It’s the moment we all wanted. Watching Clark try to keep up with Bart's speed only to realize he’s been left in the dust (literally) is a rare "humbling" moment for our resident Man of Steel.

"I'll see you around, Clark... if you can keep up." — Bart Allen

Run | Smallville Wiki