The last time I flew back from California, my seat was between a couple who rather sheepishly admitted they'd hoped the flight wouldn't be full so they could have all three. Obviously (as they were only mildly CFs who didn't actually want to inconvenience anyone else) they gave me the choice of window or aisle.
@ErrolTheDragon I've travelled with a friend and we did just that - booked window & aisle, in the hope that there'd be no 3rd person.
When he inevitably turned up, we explained straight away and offered him either window or aisle. If you do that straight away, it's not a CF thing to do.
But the couple that refused the PP to move so that they could sit beside each other, but THEN kept handing over the baby were the CFs. I would have set up my laptop on my table and sat in such a way that handing stuff over my body would not have been possible. Passive-aggressive Cheeky Fuckerism can work both ways! 