Smallville, Season 6, Episode 11: Justice League
Cyborg, Impulse, Green Arrow, Aquaman, and (duh) Superman.
This was great fun TV! Lots of comic book nods, funny banter and repartee. It was hard to see Green Lantern as NOT AC (Aquaman), but that actor did a good job, too.
This is what Smallville could be every week. Dammit.