Well, mine's a bit funny:
I have participated in a couple of jams before (two GMTKs and a tool jam), and my boyfriend wanted to try participating in one with me. The thing is, while we are planning on moving together soon, we still are living with our respective parents, so we decided to go big, risk it all and rent a short-stay apartment in another city and live together for 8 days to participate in this jam, and we're really happy with the experience and the result (although we didn't see the city that much because we were way too focused on the game)!
With regards to the game story, we originally planned on making a game about being a bus driver in a city infested with zombies that infiltrate into society that has to decide whether to trust passengers not to be zombies. Then we realized we thought of that story just because we were in the middle of an 8.5-hour bus travel to where we were staying when the theme was announced :/.
My boyfriend also thought of making a game where you play as a school teacher that gets pranked on by their students, slowly leveling up to each school year up to university. I didn't fully like the idea and was afraid of the idea being too big for the jam, so we ended up scrapping it and reaching our final idea:
The actual game we ended up making tells the story of two psychopath siblings that inherited their parents' pawn shop after their mysterious death (the idea was that they most likely killed them), and have to keep the business alive. However, they happen to be incredibly good at manipulating people to get decent deals, so they do that. We were wondering if just having a conversation simulator to get deals (or any other similar ways of implementing it) were going to be enjoyable, so I thought of making it a card game, with the excuse that they are obsessed with card games (and a bit bad at social interactions), so they gamify every conversation internally as a card fight. With the 7 customers we designed with care and love and the 27 cards, each one of one of 7 different types we thought of, that meant we would have to write over 300 unique dialogues keeping in mind the different personalities of the characters. Of course, this was too much for the jam, but we only realized at the very end of the jam, so we ended up with only 3 characters (and each only having about 7 out of the 27 card responses available), just making it playable enough.
We do plan on finishing it up as our not-so-little personal project, though!