Martian Manhunter shared a few exciting adventures with other DC Comics heroes following Smallville's ending. Played by Phil Morris, Martian Manhunter aka J’onn J’onzz was an ally to Clark Kent (Tom Welling) in the later seasons. They first met in Smallville season 6 when he had to save Clark from one of the aliens that escaped from the Phantom Zone. As it turned out, J’onzz had been on Earth for years, watching over Clark in secret on behalf of Jor-El.
Martian Manhunter ultimately became a recurring character who appeared in multiple episodes over the course of the following three seasons. In Smallville season 7, he helped Clark defeat Bizarro and lost his powers in the process. At some point, he ed Green Arrow’s Justice League off-screen, and started working with the team as a detective in Metropolis. Later, he regained his powers and fought alongside Clark, Green Arrow (Justin Hartley), Hawkman (Michael Shanks), and Stargirl (Britt Irvin) in the Justice Society two-hour special, “Absolute Justice”, which showed off his comic book accurate Martian form for the first time.
Though Phil Morris’ last official appearance as Martian Manhunter in Smallville was in the season 9 finale, the character remained active in the Justice League throughout season 10. Smallville's ending didn’t reveal what his future after the show would be, but the Smallville Season 11 comic shed some light on his later activities. After Clark became Superman, J’onzz continued to remain on Earth, even though the fulfillment of Clark’s destiny meant that his promise to Jor-El had been kept.
Martian Manhunter, who remained a member of the Justice League, helped establish a base for the team on the Moon. Later, creatures known as White Martians – who are the hated enemies of J’onzz’s people – attacked Gotham City. This led to a team-up between Martian Manhunter and Batman (a character who never appeared in Smallville). Following the defeat of the White Martians, J’onzz was among the heroes assembled by Clark to combat an invasion of Monitors in an event that was essentially Smallville’s version of “Crisis on Infinite Earths”.
His role after Smallville ended was somewhat similar to his presence in the show, with one difference being that he no longer needed to protect Clark. He was always a bit more visible than most Justice League heroes, with many of them only appearing in two or three episodes. Though he wasn’t as actively involved in Clark’s life as Green Arrow, Martian Manhunter was instrumental in his journey to becoming Superman. He protected Clark time and time again from threats that would have ended his life early. He even gave up his abilities for the sake of Clark’s survival, and secretly conspired with Martha Kent (Annette O’Toole) to keep Clark safe from Amanda Waller’s Checkmate in season 9. Unlike other heroes who always had their own problems to deal with, Martian Manhunter’s top priority in Smallville was safeguarding the Last Son of Krypton.