Maybe you have already seen this. It won a Bafta last week and it is hilarious. Be prepared to roll on floor laughing til you ache.
French and Saunders made this short film about Mamma Mia for Comic Relief, a charity show in the UK. Sienne Miller, Patsy from Ab Fab, Little Britain cast, all in thre. Brillant stuff except I can't post it here.
Here's the link. Part 1 and Part 2.
Please watch it, it's the funniest thing I have seen this year.