I HAVE A THEORY ABOUT THAT
IDK IF ITS A WELL KNOWN ONE BUT I THOUGHT OF IT A WHILE AGO (open thread) https://twitter.com/VOL6MELODY/status/1312165102792007682

okay so we know that louis was in a band named the rogue and harry was in the white eskimo, right?
and we know they was in that band competition in 2009, right?
we have a video of harry's band onstage and can hear someone who sounds like louis shouting "get on with it"

the get on with it video:

sooo we can assume they probably met each other there
SOOOOO
i know it sounds obvious but like
what if harry accidentally peed on louis, said "oops" like a normal person would do (maybe without seeing who it was?) and when louis looked up to see who tf peed on him,

he recognized harry so he said "hi".
THEREFORE
it wasn't a random oops and hi, it was like "oops sorry my pee is on you" and then "hi omg i remember you"

IM SORRY IF IT'S A KNOWN THEORY I JUST THOUGHT OF THIS A WHILE AGO