A fuddy duddy is a rather prim, pedantic, stick-in-the-mud, humourless fogey. It’s used very aptly to describe Nigel Farage, the frighteningly successful leader of UKIP, in this rather entertaining article from The Independent about his sartorial style.
It’s the sort of expression that is very difficult to translate. Maybe there are no fuddy duddies in Sweden? Swedish “slipper heroes” (toffel hjältar) certainly have various qualities in common with them.