This isn't trans-Atlantic, but in my husband's home country, nicknames are all kinds of hilarious to your average American.
For instance, we've tossed around the idea of naming a future son "Alexander." Rather than the typical nickname "Alex" (which I would expect), chances are good all of my in-laws would nickname him "Lek-lek." I think my husband actually knows someone who goes by that nickname, come to think of it. He also has a cousin of some sort who goes by "Kiki" (short for "Nicholas").
Then there's the tendency to call people "Boy" or "Girlie" or similar even when they're white-haired with grandchildren.
It's really interesting seeing how different countries are likely to nickname a person, but it seems pretty safe to say that every country has some hilarious conventions.