Recently I started re-watching the TV show Fringe, and noticed that they used different colored opening credits that indicate the universe the majority of the episode takes place in. [I am only up to season 3, but I understand they use 4 different color schemes to indicate the universes. Blue: Original, Red: Alternate, Black: Observers, Yellow: Final]
I recall that Supernatural TV show changed the opening credits designs, but AFAIR it was based on seasons. In that, each change in the opening credits indicated a new season.
The TV show Frazier also changed logos. But that was just a change of color to indicate seasons, and the random variations in the "city skyline" was just random and had no bearing on the episode.
Was Fringe the first show to have a meaningful variation in the opening credits? (Have there been any since? I cant recall any.)