Just had to share this story. There's a street of King Milan IV (the fourth), who never existed, in Kragujevac.

There was only King Milan I (the first), and his name was among the suggested new names for old streets. The whole list went to the city hall to vote, and this one passed, which someone marked with a checkmark at the end of the line. So you have an I and a checkmark... then whoever made the order for new signs, thought this was an IV... and so it is even now.