*laughs* your secret is safe with me! (I think I have the advantage; as an American I'm not really familiar with Catherine Tate - I think I'd heard the name before, but not enough to recognize her when we watched Runaway Bride or anything - so the stunt casting aspect doesn't bother me.) I'm really looking forward to Donna, because she is so different from any of the New Who companions, and I'm curious to see where she'll go, and what her relationship with the Doctor will be like...