After Smallville ended, the comic continuation killed off Bart Allen, a founding member of the show’s Justice League. In DC Comics, Bart Allen aka Impulse is a descendant of Barry Allen and the fourth incarnation of the Flash, and he made his first appearance in the Smallville season 4 episode, “Run”.

In “Run”, Clark (Tom Welling) had an encounter with a young thief named Bart Allen (Kyle Gallner), who possessed the ability to run at superhuman speeds. To Clark’s surprise, he discovered that Bart was actually much faster than him. With Bart, Clark found that it was nice to have a friend with powers similar to his. And at the end of the episode, Bart left Smallville and didn’t return until season 6, when it was revealed that he had been recruited by Green Arrow (Justin Hartley) to be a member of Smallville’s Justice League. As a Justice League member, Bart appeared again in the season 8 finale alongside Black Canary (Alaina Huffman) to assist Clark and Oliver in the final battle against Doomsday.

Related: Smallville's One Main Villain Clark Never Actually Met Onscreen

Later episodes made it clear that Bart remained on the team, but Kyle Gallner never returned to the series after season 8. The Smallville Season 11 comic book series, which picked up where the show left off, revisited Bart Allen by sending him on an adventure with Clark. Together, Bart and Clark battled Black Flash, a DC Comics villain and a powerful entity created by the Speed Force. Apparently, this creature crossed paths with Bart offscreen in the episode that introduced the Justice League. During their mission, Lex Luthor (Michael Rosenbaum) tortured Bart by forcing him to run on a treadmill without stopping. This event was depicted in the episode, but what wasn’t shown was that Bart reached a speed that allowed him to tap into the Speed Force. It was this moment that Bart drew Black Flash’s attention, which ultimately led to his death.

Bart Allen agrees to join the justice league in Smallville

Though years had passed since then, Bart was still on the run from Black Flash in Smallville Season 11. Even with Superman around, it seemed that the creature couldn’t be stopped. After a long battle, Bart decided to sacrifice himself to take down Black Flash for good. The fight culminated in an explosion that seemingly killed both of them. Clark was left devastated by Bart’s death, as the two had a friendship that went all the way back to Clark’s senior year in high school.

While it’s true that Bart Allen only made three appearances in Smallville, he was still one of the show’s most important superheroes. Admittedly, he wasn’t around as much as Green Arrow, Martian Manhunter (Phil Morris), and some of the others, but he still had an impact. Bart preceded all of them in season 4 when he became Smallville’s first DC Comics superhero guest star. At that time, Clark wasn’t expecting to meet someone whose powers had nothing to do with Kryptonite or the meteor shower, especially since most of Smallville’s super-powered characters were connected with Clark in one way or another. Bart Allen helped expand Smallville’s world beyond the characters and concepts associated with the Man of Steel.

More: Smallville: Why Clark Waited Until Season 6 To Tell Lana His Secret