3 Melanie Bush
Doctor Who
Role: Duracell-topped Who companion with photographic memory, played by Bonnie Langford.
The painful truth: In her very first scene she tries to force-feed the Doctor carrot juice and sticks him on an exercise bike. Seven episodes later he tries to kill himself, but unfortunately regenerates, and is stuck with her for four more stories of glass-shattering screaming and polka-dotted Alice in Wonderland dresses.