Season 6 extra features include deleted scenes, a gag reel, a “case closed” retrospective and two audio commentaries for the finale episode (Tim, Willie and Jeff on one side, Matt and Jeff on the other).
Note that besides a nice cardboard box, the “con-plete collection” doesn’t contain anything else that the 6 DVD sets of each season. No additional bonus there (Thank you Daclaren for the info!)
For a foretaste of the extras from season 6, click on the image below to watch a selection of deleted scenes. Password is tdktv