Usually you talk about directors in terms of the way they choose camera lenses or a kind of light to create a certain effect. But to me the most valuable commodity for a movie to create is a feeling of life, and that's what A Hard Day's Night has in spades.
It's so much fun that the money is just icing on the cake. There seems to be a lot of icing.
I remember thinking, 'I'll audition just once and if it doesn't work out I'll never think about it ever again.'