In 2004, Bart works with a fence named Hanison, although Hanison often cheats Bart out of stolen goods' true value. Bart happens to be in Metropolis when Jonathan Kent is about to get run over by a drunk driver. Before Clark Kent can rescue him, Bart rescues Jonathan at super-speed and also steals his wallet. Clark tracks his father's credit cards and locates the hotel room in which Bart is staying. Bart says to Clark, "I'll be a thousand miles away before you can even blink," and Clark replied, "I don't know, I blink pretty fast." They have a "race" in which they seem to be almost evenly matched in speed until Bart takes off over the water. Bart is amazed to find another person with super powers, just as Clark was to find someone with powers who was not from Smallville.

Bart and Clark bond. (Bart even takes to his friends, flirting with Chloe), but they argue because Clark tried to make Bart believe that stealing for any purpose was wrong. Bart believes that he only steals to buy food and shelter, and that he isn't harming anybody because the company cancels the illegitimate charges. Later, he follows Clark to the Luthor Mansion where Lex Luthor shows Clark a valuable Russian manuscript.

Bart later returns to the mansion and steals the manuscript while Clark is reading it, and takes it to Hanison, where Lex tracks it down. Hanison is willing to kill Bart over the manuscript but Clark saves him. Bart wants to make a getaway with it, even after Clark asks him if he still thinks that his thefts hurt no one, but is reminded of Clark's warning that he should use his gift nobly. In the end, he returns the manuscript and leaves Smallville to find other special people like himself and Clark. At the very end of the episode, Bart demonstrates vast super speed, during which he outruns Clark.

Two years later, Oliver Queen finds Bart stealing a meal in Star City. Oliver believes Bart is a good kid and offers him a job. Bart joins Oliver's group of heroes, and Oliver gives him the codename "Impulse" for his impulsive nature.

In 2007, Bart travels to Mexico to infiltrate a LuthorCorp facility for Oliver. He returns to Metropolis in time to save Chloe Sullivan from getting shot by Dr. Caselli. Bart then gets back in touch with Clark after a small race. He tells Clark that he has really learned what he tried to teach him, and declares that he has quit stealing. Clark soon learns that Bart had in fact stolen information from LuthorCorp, but Bart does not tell him that he is working for Oliver.

Bart leaves to do another job for Oliver, but falls into a trap set up by Lex Luthor. Lex puts him in a chamber and forces him to run at super-speed or risk being electrocuted until he agrees to talk. Clark goes to rescue Bart, but is incapacitated by refined Kryptonite. Oliver dons his Green Arrow garb and, along with his other team members Cyborg and Aquaman, infiltrate the lab, save Clark and Bart, and blow up the facility. Bart leaves with the "Justice League" and continues working to stop other 33.1 facilities around the world.