During the end credits of each show we get to see not only out-takes but alternative workings of scenes from the week's episode.
The end credits for the season's final episode, "Seeing the Light", featured scenes from all the previous episodes of the season.
At the end of the final episode ("Lighthouse Blues"), the credits do not end on the traditional black screen. Instead, they end on a shot of the cast, who yell out "BYE!"