Romania/Bulgaria is a common pairing involving the characters Romania and Bulgaria. It is also known as RomBul, BulRom or Vampire Rose which is a combination of Romania's constant acting as a vampire with Bulgaria's national flower.
Romania and Bulgaria both belonged to the Axis group, and were once under Russia's rule. Most tabloids accuse Romania and Bulgaria as the useless members of EU and they are both shown to support each other in various terms.
Bulgaria and Romania are best friends, with nearly all of their appearances being accompanied by the other.
In most fanworks including this pairing, the most used concept is Romania as a vampire while Bulgaria as a character that'll soon come contact with him.