LOS ANGELES -- James "Jimmy" Olsen may be best known for playing sidekick to his pal Superman in DC Comics canon, but in Supergirlthis season, the intrepid photographer -- played by Mehcad Brooks -- will decide that he doesn't want his Superfriends to have all the crime-fighting fun.

"James is going to decide that he can no longer sit back and be a sidekick, so he’s going to decide to become a vigilante -- he’s going to become Guardian, complete with the shield," Supergirlexecutive producer Andrew Kreisberg told reporters at a Tuesday screening.

In the comics, Guardian was Jim Harper, a cop turned vigilante with no super powers who wielded an indestructible shield. A character called Jim Harper was introduced in Season 1 of Supergirl, but he apparently won't be donning the shield.

James' new alter-ego will cause "a massive problem" in his relationship with Kara (Melissa Benoist), Kreisberg said, because he's decided not to tell her, at least initially. And we all know how well secrets work in superhero shows.

"Now there’s this new masked vigilante, and she has her own feelings about vigilantes, and it becomes a push and pull about who gets to decide who gets to be a hero," Kreisberg said.

Kara might not approve, but another member of Team Supergirl is definitely on board with James' transformation: Winn (Jeremy Jordan), who also underwent a big change in Season 2 when he left CatCo for a job at the DEO.

"Winn is his man in the van," Kreisberg teased. "He takes this job at the DEO and then is lying to everyone about how he's spending his nights because he's going out with James."

Supergirlairs Mondays at 8 p.m. on The CW.