The plot: Comics legend Alan Moore wrote arguably the definitive Mongul tale (while there are various incarnations, he's generally a punchy, hefty alien warlord) in a story that turns Superman against his friends. Batman, Robin and Wonder Woman arrive at the Fortress of Solitude with presents for Supes' birthday, only to find him enslaved to Mongul by a plant that traps him in a walking nightmare.
The gabillion dollar setpiece: Superman turning on Mongul after awaking from the mind-control, and battling him across the Fortress of Solitude while Batman and co battle the mind-control plant.
Chance of happening: 40%. It'd take a hefty amount of story-wrangling to get Batman, Robin and Wonder Woman to appear on-screen, but their characters are pretty interchangeable. And Mongul's a decent enough Big Bad to ensure at least part of the story is incorporated into his on-screen origin.