well, beside some cultural traits(which we could see are more international than we thought), I'd be interested in some peculiar linguistic links. As an ordinar romanian, i don't know much. It is known that in the communist period it was a kind of "agreement" between the countries, about their official history. specific, between romanian and bulgaria, it was a common "interest" that hide proofs of romanians history on south Danube. Instead, bulgarians agreed to deny any bulgarian trace at north danube. So, the lingvistic linc between romanian or bulgarian were posibly hidden, or marginalised. After 1989, i've heard from more or less specialists from neighbour countries(even from more distanced countries), the accusations that romanian specialists, in 19 cnt, banned a lot of slavic origins words, replacing them with neologisms from french or italian(which is not quite true-I know about 15% slavic words in our lexic since communist times). But taking in consideration their accusation the ratio was much more higher, I followed the subject. First thing I discovered, it was an objective thing: in fact slavic ratio becomed much more smaller, due to technical term, who make the lexic to increase dramatically. but this happened in every country(even slavs imported much from french). The day by day lexic, didn't decreased too much. Other thing I discovered, was that some regionalisms dissapeared, but it was a natural effect of the union of romanians. another thing: some words(not many) were treated by romanian dictionary, as dacian or latin origins, even it was clear they were slavic. Today, these sincopes dissapeared.
From the slavic words of romanians, many could comme from bulgarian, or slavonic(official church language) but, also from serbian, slovak, ukrainean...The romanian dictionary recognise them like this, with the mention that when we say slavonic, it could be implied any other slavic language-nothing is sure. About the link between bulgarian and romanian, could be, then, two categories: slavon origins(majority), and "bulgarian" origins. Those "bulgarian" origins, when I've checked, can't be found in any other slavic language- that could means that are from proto-bulgarian origins.
here is a video from a bulgarian, more or less nationalist, from Romania:
YouTube - ‪In limba Romana "B" cu cuvinte bulgaresti !‬‏
He present a list of words which begin with "b" in romanian, giving their correspondent in bulgarian, wishing in this way to show that "in words with "b" are such many, we could imagine the entire lexic. The video has some amusing things: he pretend words like "bulgarian", or "bucurestian" to be from bulgarian origins. But searching the list, I observed:
- the majority of the words are from slavic origins(and derivates);
- some are from "bulgarian"(proto-bulgarian, as I've asumed):
rom: rochie(rokye), bulg: roklija
rom: bolovan(stone), bulg: balvan
rom: breaz(virtuous), bulg: briaz
- some are from latin origins:
rom: biserica(church), bulg: tzarvka
rom: boci( to wail), bulg: bucy(butchy)
- some are from unknown origins, which could means are from daco-thracian origins:
rom: bot(snout), bulg: hobot
rom: bura(drizzle), bulg: buria
rom: bubui(to bang), bulg: boboti
- some are from greek origins:
rom: boboc(bud), bulg: bebok
I am not bulgarian speaker, nor I know how they are deffined by bulgarian dictionary, but since he is bulgarian speaker, i think some could be true. And since only those who begin with "b" are these, it could be many.