It was actually briefly mentioned by Qyz in another topic: There's the snapshot =P This also happens in the GBA version, but it goes from right-behind to the left side of DK Island; makes more sense.
After playing the game billions of times, one has to notice such things :D I definitely noticed it, I don't remember when I first did, though. I was two (ish) when the game came out, so I'm not sure when.