Why Every Modern Companion Left Doctor Who
12. Catherine Tate - Donna Noble
Nobody expected Catherine Tate to sign on for one season, let alone two, which is largely why she left at the end of season 4!
Due to the massive popularity of Tate's sketch show, and a pending transition between showrunners Russell T Davies and Steven Moffat, she was only contracted for one season as Donna Noble. But just because we all expected Donna to leave at the end of season 4, did the departure have to be so shockingly BRUTAL?
Of course, Donna would make further appearances in Doctor Who - alongside the other RTD era companions - in The End of Time and eventually, her tragic ending would be put right in the closing moments of The Star Beast.