Two Harry Potter Eras Stuck in an Unknown Room ~HP Fanfic~

What happens when two eras of the Harry Potter universe are stuck in a random room with no explanation, and don't know how/are unable to leave? What happens when you don't know half of the people with you, but one stranger looks like a wannabe version of you but with different eyes? What happens when you see two men, see young versions of themselves along with a younger rat, their dead friends, dead classmates, and baby versions of young adults in your time? What happens when Fred and George meet Fabian and Gideon? Will the truth of who is in the room with them, get revealed unintentionally or will magic itself tell them? What is the room for, will they do anything, or will they just be stuck? Is magic allowed, if so will their be duels or funny quips? And what about the guest list- who qualifies? -What year are the people from both eras from? -Who are the other dead friends? -Will Harry believe that his parents are there, or will he try to deny it? -Will this send Sirius into the insanity that Azkaban somehow didn't rub off on him? -All this and more answered and shown through "Two Harry Potter Eras Stuck in an Unknown Room ~HP Fanfiction"