Go to the scene where Potato Head exclames,"I'm paccioso!"(scene 3 for dvd users) Look at where his parts are placed. The only way they could be there is if he had new slots.
Potato head says "Picasso". The joke isn't in the fact that he's a potato, the joke is in the fact that all his parts are mixed up, imitating the cubism Pablo Picasso's art was so famous for.
It doesn't matter exactly what he says, the slip-up is that in order to have all the pieces where they are, he would have had to drill a few new holes.