Perhaps Bill Cipher annoying Stanley or another member of the Pines family. (Or if you feel up to multiple, everyone e within the Pines family. Only if you want to though)
It was Halloween, they were in Central City for some candy pickings (if their fathers know, it's too late, they're here and absolutely getting that stomachache in the morning once they're done here.).
Jon— Superboy had Robin in his grip, flying from apartment complex to houses, one ear out for flash, incase the hero accidentally stumbles upon them.
(He's doing some extra patrol, it was Halloween after all.)
It was spooky day and when they finally rest up on a roof, rummaged through their goods, did Robin and Superboy notice the glowing skull at the bottom.
It looked like it could be from gotham, honestly. It was creepy, dirty and Jon has it in his hands, studying and playing with curious spark in his eyes.
"Put that down superboy—! That's clearly cursed!" Robin warns, trying to take the skull, yet the other dances from reach.
"If I rub it 3 times, do you think I get 3 wishes?"
"Those are genies you're talking about, not skulls!"
Not waiting further nor listening, really, superboy rubs the skull 3 times and—
Nothing happens.
"Nothing. Will you pit the damn skull down now?"
Sighing, Superboy does so, until the skull starts glow.
And glowing it is, a bright green, frost growing along the ground and it was beginning to eat the entire apartment if they didn't do anything!
As the cool mist grows, they step and tense as a figure approaches through.
"Congrats, no idea how but you guys found Pariah Darks former skull! So much less work for me now."