Board Thread:The Panopticon/@comment-1293767-20151029072618/@comment-5918438-20160111181452

So 10% is definitely a solid rule. The End of Time timecode is within part 2 specifically, right?

(On a side note, you're a god ;))

Can anyone think of any valid guest characters who appear only right at the end of episode 1 and then play a large role in the second episode? Just wondering.

Oh. Right. Also: We've been using the terminology of "guest character" for a while now in this discussion, but "guest cast" here specifically means non-recurring. Recurring means having appeared in more than one story.

This would technically discount Ashildr for The Girl Who Died/The Woman Who Lived, as well as River Song for The Pandorica Opens/The Big Bang. And you can't make the case that TBB has no guest characters beyond those recurring, because of the scenes back to Amelia's childhood.

But the non-recurring rule is important to weed out Miss—ohhhhh. Okay, idea. Extend the last 10% rule to also include a maximum of X% at any time in the episode, so as to exclude very short series-arc-related appearances in otherwise unrelated episodes like those of Missy in series 8, and of Kovarian in 6a.

Then we can drop the "guest, not recurring" language and simply exclude any character which appears in the majority of episodes in its series run. This also discounts Danny Pink, I think, in series 8. In split series, the "series run" is half of the total series. So that still excluded Amy and Rory in 7a, and Clara in 7b. And Kovarian in 6a. And Missy in series 7, come to think of it.

Sadly, Jack Harkness doesn't quite make 50% of series 1, so maybe a continuous run of at least 4 episodes can count as well? If Jack counts as a linking character, then Boom Town is part of a three parter. I don't think he should be, though, because he's clearly part of the TARDIS crew, even though he was introduced late. So too, Mickey was a companion in series 2, despite leaving early. Both appeared in a continuous run of at least 4 episodes (for Jack, 5). I don't suppose they're both listed in the pre-title sequences while they're companions?