I originally had this idea as a joke, but I guess I'll post it.
What if, when another PC yawns, there's a chance yours will as well? Just like the IRL phenomena of contagious yawning! Possibly only if you've directly decided to "watch" them, to prevent it from getting out of hand.
I held off on suggesting it because I can only imagine how spammy it would get during Town Halls, but the idea to only have it work if you're directly "watching" someone could mitigate that.