I was on a Ryanair flight recently during which this guy (about 25) spent most of his time doing some kind of mad dance in the aisle punctuated by the occasional bit of loud "singing". He also hammered on the toilet door a couple of times "for a laugh". The FAs sidled past him and asked him to move aside for the trolley when they needed to pass him, and he complied readily enough, apart from that they and everyone else completely ignored him. Lunatic behavior completely normalised.