Smallville :

In this special episode, Oliver Queen, aka the Green Arrow, sends out for reinforcements and Bart Allen, aka Impulse; Arthur "AC" Curry, aka Aquaman; and Victor Stone, aka Cyborg, return to Smallville to help Oliver take down a secret LuthorCorp laboratory.

During a break-in at the facility, Bart is captured and tortured by Lex, but when Clark tries to rescue him, he is felled by meteor rock. An alarmed Chloe goes to Oliver for help, and the newly formed league springs into action to rescue Clark and Bart.