Imagine Cap's identity reveal happening years later when he's already over 18. Like, they would have been working together for a whole decade, laughed together, cried together, introduced him to their spouses etc and then suddenly. Boom, lightning, and he's actually some college kid. The whole League immediately starts panicking and doing the math in their head while Billy's just like-
"Statue of limitations", with a shit eating grin preferably. Come on, he's been losing sleep over this for years, now's their turn to let it mess with their heads.
Imagine them calling it a day and going home, trying to relax after that hectic mess and then it suddenly hits them-
Clark staring at the ceiling in his pajamas, "I punched a 10 year old once. And really hard too."
Wally stress eating cereal, "I always liked the guy because I felt we were on the same wavelength. What does that say about me that I can hang with a literal sixth grader and not even mind? No, wait, don't answer that."
Arthur venting to Mara, "I had lengthy discussions trying to convince a twelve year old to go out for drinks, on multiple occasions."
Most of Young Justice, "he's younger than me and he's been the on-and-off again den mom for years!"
"Oh! btw guys, it's my birthday today!"
"Oh, wow, all these years and you never told us, happy birthday man"
"Thanks!"
"mannnn 'all these years' is RIGHT, I've got grey hairs and a permanent backache. I'd swear you haven't aged a day Cap, what's your secret?
"magical transformation sequence. I have two 'forms'; my other one has been aging this whole time."
"ah, damn, guess not even demigods are so lucky as to have eternal youth, huh? how old are you now, anyways?"
Billy:
"Eighteen."
