While on Smallville, Green Arrow was the one assembling heroes, in The Batman it was the Martian Manhunter who was assembling superheroes. The Batman had the Dark Knight beginning as a solo hero, then teaming with Batgirl and next Robin. In 2007, beginning with the season 4 finale, Batman went from mentor to member of the Justice League to fend of, you guessed it, alien invaders.
Batman and the Martian fended of the invaders and in the last scene we met Flash, GL, Green Arrow, and Hawkman.
It wasn't until the season 5 opener that the crown jewel of the JLA was introduced, Superman. Throughout the season, Batman teamed up with team members, and then in the series finale the whole League was enlisted to fend off once again those pesky alien invaders.
Up Next: Justice League: The New Frontier
The Superman/Aquaman Hour of Adventure * Super Friends * The All New Super Friends Hour * Challenge of the Super Friends * Legends of the Superheroes * The World's Greatest Super Friends * Super Friends (Shorts) * Super Friends (Lost Episodes) * Super Friends: The Legendary Super Powers Show * The Super Powers Team: Galactic Guardians * Justice League of America (TV Pilot) * Justice League Unlimited on Batman Beyond * Justice League * Justice League Unlimited * Smallville * The Batman