1. Married couples always sit separately as wedding guests. On the other side, engaged couples sit next to each other.
2. Unlike the rest of the world, Swedes wait from one all up to five weeks to hold a funeral after death.
3. Personal titles like Mr (herr) and Ms (fru) are very rarely used. Miss (fröken) is considered to be archaic and even impolite, but sometimes it is still used for nursery teachers. Unlike in German, French or Slavic languages (Sie, vous or Vi), plural You (Ni) is not used.
4. You can wear a national costume to a white tie event. It is not uncommon to see Swedes in national costumes at PhD graduation ceremonies or royal events.
5. An important part of all kinds of festivities, including formal dinners is singing drinking songs (snapsvisor). Every Swede learns at least a few of these short and spirited songs (e.g. unavoidable Helan Går) as a student.