<P> Although the Justice League first appeared in season six 's `` Justice '' , each member had their own introduction and recurring storylines in the series prior to the formation of the team . The first member to appear on Smallville , other than Clark Kent ( Tom Welling ) , was Bart Allen ( Kyle Gallner ) , who was introduced in the season four episode `` Run '' . In the episode , Bart is the first person Clark discovers to have a superhuman ability -- being able to run at supersonic speeds -- that was not created from exposure to kryptonite . When Clark and Bart first meet , Bart is a pickpocket who saves Jonathan Kent ( John Schneider ) from being hit by a truck . Eventually , Clark convinces Bart to give up his life of crime . Arthur Curry ( Alan Ritchson ) , who has the ability to swim at superhuman speeds and create energy blasts through the water , is next to appear in the season five episode `` Aqua '' . Arthur arrives in Smallville to stop an underwater weapon developed by Lex Luthor ( Michael Rosenbaum ) , which is killing the surrounding ocean life . Arthur and Clark initially clash on Arthur 's tactics ; Arthur tries to blow up Lex 's lab , while Clark insists that they should simply talk to Lex face - to - face and ask him to stop . Eventually , Arthur and Clark locate and destroy the weapon outright . Season five also introduced Victor Stone ( Lee Thompson Young ) in the episode `` Cyborg '' . Here , it is revealed that Victor was mortally wounded in a car accident that also took the lives of his family , but Lex 's company , LuthorCorp , took Victor 's body to a research lab where they experimented on him -- ultimately replacing his bone skeleton with a metal one . Clark attempts to provide Victor with a safe haven after Victor escapes from Lex 's facility . Clark manages to convince Lex to stop hunting Victor , who eventually leaves Smallville with his girlfriend . </P>
when does clark meet the flash in smallville
the season four episode `` Run ''