I watched this yesterday and when Maddy was listening to the cd, I yelled "well, there's a big gaping plothole" at the TV. And then they gave this explanation about Frank willing the cds to Billy to cover it up, which I thought was pretty neat, considering he could have left them all to Sullivan. I could see Frank letting him in a little bit at a time and when he realized that Billy wasn't the rat, he seemed so happy.

BTW, I think the movie would have had a completely different feel if it was either French and Saunders or Abbot and Costello. Maybe that's an AU worth exploring ;-)