Now he likes to put the wrong tail end onto the head a say "no no cocka-do-do(or whatever the animal was supposed to be)". He also likes to make them with the wrong side facing up: "u(p)-si(de)-dow(n) do(g)"
He's got a bunch of 3, 4 and 6 piece jigsaws (though he is singularly uninterested by the 6 piece dinosaurs, and will chose a 3 piece train over them every time), but his absolute favourite is this:
In a bag of clothes from second-cousin Nicholas was the most marvellous tractor puzzle! It normally takes Nathaniel a maximum of two minutes in the living room before he is carrying around the tin case that contains the "tracta-da-da pu(z)". And he's getting pretty good at putting it together. He can manage about a third on his own, but hasn't quite got the knack of finding the right pieces to link the section with the wheels with the section with the farmer. But all you have to do is suggest pieces and he goes and tries them in appropriate spots and lets you know "no no no" if it is the wrong position.
He has his own way of taking it apart at the end!