Ghostbat hc:
Batman should casually threaten others with ghostmaker's name. He always did but in a batdad-joke-y way. Like, one time, Aquaman, from being under some mind-control that they hadn't discovered then, became a bit violent towards the JL members.
He slams Bruce against the wall (do not get naughty thoughts 🧐), and applies way too much pressure with his forearm, against the bat-armour. Batman can feel the incredible stress on his chest. No matter how strong the armour, Arthur is still an Atlantean. They both know it, and this is what makes J'onn realise that something is terribly wrong here. This is not how Arthur behaves, even when he is agitated. J'onn slowly tries to break the mind grip, without alerting him too much. He might react even more aggressively. The spelling is broken by J'onn, of course, but not before Batman warns Arthur, "If you kill me...a ghost might hunt you down, and eat you alive piece by piece." After that, when Arthur feels very sorry for hurting others, especially Batman. They all console him that it's not his fault. B casually comments on how he needs to improve his armour, and that in a way Arthur helped him improve the batsuit. Everyone did think that the ghost hunting line was very odd, but this is Batman. He is an odd person and has an odd sense of humor. They just see it as one of them usual bat-shenanigans and quirks.
Years later, when the JL members finally meet the ghostmaker...Aquaman is the only one who remembers the weird ass comment from Batman!
Aquaman: "Oh!! So, you are the GHOST."
Ghostmaker: "...???"
Batman: (just realising a second too late what Arthur is gonna say) "that'snotimportantrightnow."
Aquaman: "Batman once said if I kill him, a ghost will haunt me and tear me apart. I thought that was a joke but--WHAT THE --WHAT ARE YOU DOING?!!?!!?"
Everybody calm down. Ghostmaker wasn't trying to headbutt Batman. He just got a bit too excited, and tried to kiss him, right then and there. It's just that he forgot he got a whole ass, full helmet on...