A long time favorite of mine was a bug, design flaw an inherit flaw born out of laziness. The word is, the designers of Sherlock Holmes versus Arsène Lupin did not want to animate the walk cycles and thought it would be far easier if Sherlock's olde chum simply appeared behind him.

They were correct, it was indeed far simpler. However what they did not take into account was Watson's new creepy personae. This video captures it excellently. And, on a related aside, reminds me of my wife. Who, much like Watson, has the habit of simply appearing behind me at any given monument. In fact, as I write this, I am unnerved to look over my shoulder.