These dishes are very popular in Slovakia, though I have never seen them anywhere else. They are very simple to make, and quite tasty.
In Slovakia they are made with flat (ribbon) type noodles, though there is no reason they could not be made with just about any kind of noodles.
These are main dishes, not side dishes.
Poppy seed noodles
This is the most popular type.
Simply grind the poppy seed, mix it with powdered sugar, combine with boiled noodles, and mix well again. You may pour some melted butter over each individual serving.
Cottage cheese noodles
Very simple to make, very delicious. Just mix some fine-structured cottage cheese with either some salt or some sugar, and mix it up with boiled noodles.
I will never forget the noodle war I experienced in a boy scout camp in 1970. We decided to serve cottage cheese noodles for supper one day, but the campmaster made the mistake of asking the scouts whether they preferred the sweet or the salty variety.
Well, about half of them wanted sweet, the other half salty.
All day long the kids were yelling the words sweet and salty as a battle cry, while hitting their metal camp bowls with their spoons (that was long before "there is no spoon" became popular).
We ended up fixing both, so eventually the noodle war ended up in peace with everyone busy eating their favorite.
I chose salty that day, in case you're wondering.
Not as common as the above, but just as easy to make, and just as good.
Just mix up some fine chopped walnuts with some sugar, and mix it all with boiled noodles.