Board Thread:The Panopticon/@comment-1293767-20151029072618/@comment-1293767-20151125165328

Bwburke94 wrote: Also, as a reminder, we should write this so episodes shorter than 20 minutes can't be joined to episodes 20 minutes or longer. They would more likely be tagged as prequels even if they include TBC.

That's a good point I hadn't even considered. Moffat did say pre-series 8 that there would be more "short episodes" (minisodes in varying lengths) due to the popularity of Pond Life and The Night of the Doctor. It's conceivable they could add a TBC to prequels/minisodes/short episodes in the future. They randomly apply them to full length episodes, so I wouldn't be surprised, but I also would not want to count something like that as a multi-parter with a full length episode if they got an itch to do so.