clark kent grew up playing football and baseball. after a good play in these games, it wasn’t uncommon to give/receive a slap on the ass, a wordless way of saying good job. everyone on his teams did it, and clark participated, too. it was simple, quick, natural. clark never thought anything of it.
and he’s never gotten his wires crossed before. at work, he never really has the instinct to do it—there’s nothing physical about the effort he puts in at the planet like there was playing sports.
but superheroing is physical. most of the time, superman doesn’t work in a team, except...sometimes he does.
it happens on the heels of a surprisingly uplifting battle. the league isn't exactly new, per se, but they've struggled to find their footing with each other. but this time was good. minimal damage, zero casualties—they accomplished exactly what the league was made for.
it makes clark proud. proud of the team, proud of himself, proud of the work they'd done together. and batman was incredible. he'd strategized on the spot and sent everybody to perfect locations, while holding his own against the robots that were plaguing the city. between his own skirmishes, clark couldn't help glancing over to watch the powerful breadth of him get to work.
so when he lands on the rooftop where the others are gathered, it's pure instinct to lean closer to batman and clap him on the shoulder, and then his ass and say, "great work!" because that's what he does, what he's always done, when a teammate does well.
it takes a moment for his actions to catch up to him, but by the time they do, everyone else has frozen, staring at him like he's grown another head. clark himself goes entirely immobile, a hot flush of shame crawling up his face.
what can he even say? it was a pure lapse of judgement; he forgot who he was—forgot where he was, who he was with—
"kal," batman says, stretching his name out.
“i’m so sorry!" clark blurts, voice pitching upward, "that was pure instinct—!”
“you slap ass on instinct?” green lantern interjects, doubling over with laughter.
clark opens his mouth to defend himself, but he pauses before any words come out. superman didn't grow up playing human sports, couldn't have learned a human gesture like that. gosh, he's so screwed.
"perhaps we should circle back to personal boundaries in the next meeting," diana says, raising a brow at clark. behind her, the flash has two hands over his mouth, but clark can still hear the laughter in his throat.
clark is absolutely, utterly mortified. he whirls back to b, guilt twisting the line of his mouth. "i am so, so sorry," he says again. "i should not have done that—i don't know why i did that—but please believe me when i say it will never happen again."
the apology is somewhat undercut by GL still laughing at him.
but batman just sighs, his shoulders dropping. "it's fine, kal. you clearly weren't thinking."
in the background, GL and flash start protesting, insisting that clark face a proper punishment (re: verbal dressing down), but clark is happy to tune them out over the swell of relief.
batman said it was fine. batman isn't mad at him. clark knows what the shape of b's ass feels like under his palm. he's doomed.
clark apologizes again for good measure before he sets off to leave, shaking those thoughts out of his head. flash is still laughing at him, and GL is still complaining about a harsher reaction, but diana smiles and waves goodbye, so clark takes it as permission.
except, the moment he turns his back, he feels a quick swat directly on his ass.
"don't let it happen again, boy scout," batman growls, officially even.
clark squeaks and goes bright red in record time. as he flies off, GL's laughter—now delving into genuine cackling—follows him home.