Greece is a minor character in the comics, despite being such an influential nation from history.
Like many other nations, he likes to drink, as well as compete in Eurovision. At one point when he was low on money, he tried to blackmail Germany into giving him money in compensation for all the treasure and priceless arts that Nazi Germany stole from him during World War II. When this failed (as Germany had already paid him back as best he could), he demanded that he at least be given a "thank you" for the stolen goods, to which Nazi Germany vehemently refused.
He seems to be the only country aware of the existence of Atlantis.