Daniel Radcliff/Emma Watson/Rupert Grint

[potioncat]

Carol: 
> Carol, who could see Richard Griffiths playing Slughorn is he weren't
> already established as Vernon Dursley


Potioncat:
Wouldn't that be a wonderful role for him! I've caught Griffiths in a 
few other roles lately and have just begun to realize what a fine actor 
he is. He would be perfect for Slughorn!

I also think Miriam Margoyles (not sure of spelling) would have been 
good as either Aunt Marge or especially as Umbridge...of course, she 
was cast as Prof. Sprout before we knew of either character.