When I was writing Doctor Who stories, I started planning ahead. For example, in the second episode, they pick up Steam, the survivor of a ship crash on a hostile planet. He joins the team, and he’s clearly hanging with the Doctor because she’s a lot of fun, and he has a crush on her.

ANDREA: You know she used to be a dude.

STEAM: Even better.

But Andrea and Steam start flirting, and one night they get drunk in the TARDIS pub and fall into bed with each other.

Somewhere, a number of stories into the narrative, Steam gets shot and collapses in the TARDIS control room. His last words are “Didn’t want … you to … to find out … this … this …” and then he explodes into yellow light. When the light fades, there is a blonde teenage girl in Steam’s clothes. She looks at her hands and says, “Looks like I have to go back to calling myself Missy.”

I haven’t figured out the Mistress’s plan, maybe one day I will. For now, here’s her character poster. She’s going to be like Cher from Clueless, only evil.