Stir the Norwegian's porridge
To insert unnecessary chaos into a situation. To escalate matters. To absolutely wreck someone's entire world possibly forever.
Fred: Just don't mention her ex-boyfriend when you talk to her. You'll just stir the Norwegian's porridge.
Jake: Got it. The last thing I want to do is to make a scene.
Jake: Got it. The last thing I want to do is to make a scene.