Unhappy Batman/Superman sex pollen story.  They have sex until it wears off, and then Batman snaps back to being all business while Clark's still trying to bask in the afterglow.
Bruce: "We were affected by some form of pollenated aphrodesiac."
Clark: "...Did you just say sex pollen?!"
And Clark's way confused by Bruce because he can hear that Bruce's heartrate is elevated from still being turned on, but Bruce is acting like it's all just business (he halfway thinks it's Bruce being traumatized, but he literally does not act any different than any other day on the job, either positively or negatively).  And of course he can't get Bruce to talk about it, and works himself up about it because he thinks Bruce is traumatized from the sex (he isn't), and then...something happens, and Clark realizes it's not about him, it's about Bruce's issues and his devotion to the Mission to the exclusion of everything else, and it ends up unhappily but at least they can still work together.