30 Day TV Challenge Rerun Day 27: Favorite Two-Part Storyline

This challenge was produced with the help of Mr Ixolite for the prompts!

We covered the whole cliffhanger and follow-up episode thing earlier in this run of the challenge, so today we’re looking to talk about the two-part stories that we get within a series. Depending on the kind of show, these tend to be some of the biggest episodes in terms of advancing the larger storyline or simply bringing out game-changing information. Which one delivered the best for you?

Bonus Prompt: Which two-parter just botched its potential completely?