The idea is to set up a fun, mysterious occurrence that players have to figure out what they're doing to cause it. That means the effect, be it boon or bane, shouldn't be too extreme, because you expect it to happen multiple times. Also, the trigger should be something easily discoverable, or frustration will be the only thing triggered.
So, for example, every time someone asks a question in a room a gong sounds and players gain 5 pounds.
This means we need to generate both possible triggers and possible amusing affects. I think the latter is easier and I'll leave it to you. The former is trickier because it balances on the border of in-game and out-of-game actions. I guess the fancy way to put it is that these actions are at least potentially diegetic. They have to be things it is plausible for characters to do even if it is players doing it without thinking about their characters. Here are some possible ones I thought of:
- ask a question
- say a name
- say a direction (n,s,e,w or right, left)
- use a conditional (if we . . . ?, will you . . .?)
- character rests, sits or lies down.
- player eats something (this is clearly out-of-game, but might be funny.. a gong goes off every time someone grabs a pretzel)
The majority of these are just talking, but most actions would involve touching and are pretty standard dungeon fare, like opening a chest or door triggering something. They would have the mystery of what is causing this. Eating, drinking, praying or reading in the room might work, but then you have to hope players might actually do those things. I suppose it's a fairly niche application. But it could be fun. Let me know if you can think of any potential triggers.