As I was growing up, my family had a couple of sayings I took for granted were universal, at least within my language. As I became an adult I have learned that these are not universal at all:
the ketchup effect. It is an expression meaning that when things arrive, they all arrive at the same time. Think of an old school glass ketchup bottle. When you hit the bottom of it, first there is nothing, then there is nothing and then the entire content is on your food.
faster than Jesus slid down the mount of olives. Basically a saying that implies that the mount of olives is slippery due to olive oil and Jesus slipped.
What you lack in memory, your legs suffer. An expression meaning that when you are forgetful, you usually need to run back and thus your legs suffer.
You might already heard this one but I didn't learn until a relatively recent internet meme that its only here in Norway that something being "complete texas" means its completely chaotic and messy.
Also I'm using "what the fir forest" ("hva i granskauen") as a replacement for "what the hell" and I have no idea where I've picked it up.. Nobody else around me do, not even family. Works just as fine though against pain and annoyances.