iirc in Hinduism there's something called Kalpa, which is the period of construction till deconstruction of universe. So based on that lore, before big bang there's a compacted universe, maybe? Something like a seed.
Perhaps before the Big Bang, there was H.O.T. and DBSK. I don't really know about older boys group though... KPOP fans might know about this better than me.
Chuck Norris or maybe another universe which was preceded by another universe hehe as it will follow when this universe crumbles and shrink to a small mass and the next big bang is triggered , but what was it in the very first big bang ? Chuck Norris haha In a more serious tone the topic made me remember " The last question" by Isaac Asimov , very short story nevertheless quite interesting.
In the beginning there was another universe then bang a being from an incredibly advanced civilization pressed start on a VR simulation. Thus giving rise to you and me. This honestly is a legit scientific theory supported by some researchers.
Before the big bang, there was a piece of string. After the big bang, the piece of string become strings.