Doctor Who: 30 NuWho Characters Who Would've Made Fantastic Full-Time Companions

Appeared in: Under the Lake/Before the Flood.

Apart from her ingenuity at returning the base to day mode, we really only get to know O'Donnell properly in Before the Flood - how dare she be demoted for dangling a colleague out of a window!

She smiles at the Doctor almost adoringly when he's deducing things, and when he idiosyncratically checks what year it is in the same manner you determine which way the wind is blowing. Her TARDIS reaction is infectiously gleeful:

"It's bigger on the inside, it's bigger on the inside, it's bigger on the inside. How can it be bigger on the inside, Bennett? Okay, let's roll."

This is just like how we would be: playing it cool in front of The Doctor, but then letting all that excitable childlike emotion out in front of others.

O'Donnell's death is quite harrowing. The spectral shadow of the Fisher King looms over her before she turns around in terrified realisation, followed by the sound of a guttural roar and the monster's blaster, and then O'Donnell moaning in anguish. Shortly afterwards, Bennett, quite rightly, scolds The Doctor for his lack of action in trying to prevent it from happening.