DW Companions as PCs: Dodo Chaplet

Vicki leaves early in the third season, not long after Steven's arrival. She's initially replaced by Katarina, a Trojan handmaiden who is utterly clueless about anything invented after about 1250 BC. She dies only a quarter of the way in to her first proper story, deliberately sacrificing herself to save the rest of the party. (Marking possibly the only time in Doctor Who history in which a cliffhanger is resolved by the character that's being threatened with death... dying). Which suggests she's either an NPC, or her player got bored with her really quickly.

Next up is Sara Kingdom, snappily dressed special agent of the Space Security Service. Sort of an Emma Peel with a uniform and a laser pistol. (Almost literally - in the real world, the character concept was inspired by Cathy Gale, Mrs Peel's predecessor). A combination of bad planning and lousy dice rolls ensure that she doesn't reach the end of her first story, either. Although dying in the same story that she appeared in hasn't entirely stopped her showing up in some licensed spin-off media, she, like Katarina, is difficult to fit into a campaign that sticks to 'official' continuity.