The weirdest thing happens when two very different languages seem to share the same "feeling."
For instance, at least to me and other Spanish native speakers I know, Greek sounds very, very much like some varieties of European Spanish (not only because of similar phonemic inventories with characteristic dental and velar fricatives, but even intonations are similar). When I run into some Greek speakers, it takes me a while to realize that I'm not listening to Spanish at all and, in fact, I'm not understanding a single word they are saying.