One aspect that is obvious, and something said in the collection's various interviews, as well as the episode intros done by Jared Padalecki and Jensen Ackles (Sam and Dean, respectively) is how much more further the animated version can go beyond what was possible on a live-action television budget.
What is interesting about Supernatural: The Anime Series is that it isn't just a rehash of the other show. Instead, it is another interpretation of those events, another perspective, if you will. While there are several episodes in this series that are remakes of those found in the first two seasons of the American series, even those episodes will be different or have unexpected twists. This, of course, means that even hardcore fans of the live-action series will have a few surprises.
The collection starts off with "Alter Ego," a rework of "Skin." This episode not only hints at the brothers' origin stories, but also goes through the motions of one of the show's early hit episodes where a shape shifter is causing trouble in a small town. This episode is such a great showpiece for how the anime can differ and take advantage of the medium because it has a much better reveal of the shape shifter's true form in the end.
Similarly, "Roadkill" follows the live-action episode of the same name pretty closely, until the end when the development team at Mad House studios decide to throw in an extra twist for those fans who feel they already know what to expect.
Supernatural: The Anime Series has quite a few original episodes as well. One episode actually goes back in time a bit to show Sam while he is still in college and just meeting Jennifer. At the same time, Dean and their father start to investigate a Bloody Mary haunting in the same area. When Sam gets a whiff of the possible haunting, he starts his own investigation, never quite realizing that he and the rest of his family keep missing each other, which is exactly what their dad wants.
There are also a few highly Japanese-influenced new episodes in this collection. One has a Japanese river sprite known as a Kappa having some fun with Dean, but of course, in order to say the series truly covers the first two seasons of Supernatural, it has to hit on a few key points. The focus of those two seasons was the hunt for the Yellow Eyed Demon and the realization that there were several kids that were infected by his mingling, not just Sam. Throughout this collection, we will meet some of those characters, and in the end, they will all converge in one location set forth by that same demon in order to see which is the strongest and which shall lead the army of Hell.
Supernatual: The Anime Series is a unique piece of work that will hopefully inspire more translations of the like. Not only will it help to pull anime fans into the Supernatural series, but also those fans of the series that wouldn't normally watch Japanese animation into a different style of storytelling. It also helps a lot that the English voiceacting is still done by Padalecki and Ackles. As for the Japanese versions of these characters, Dean is played by Hiroki Touchi and Sam is voiced by Yuuya Uchida who both have extensive experience in the voiceacting world.
Special features include a two-part featurette about the making of the series and what kind of hurdles the development team went through for this unusual project, as well as a slew of interviews with everyone from the co-directors to Padalecki, Ackles, Hiroki Touchi, Yuuya Uchida and series creator, Eric Kripke. They are all interesting, though I have to warn those readers who aren't into subtitles, the interviews with the Japanese cast and crew, as well as the featurette, are in Japanese.
The other added benefit, at least of the version I watched, was the fact that it was all on Blu-ray. The animation just pops and the dark shadows, something not normally seen in anime, just add to the overall mood of the series. This combined with the same soundtrack fans are familiar with in the live-action series makes the Blu-ray version the preferred media for Supernatural: The Anime.
In the end, this series is well worth the purchase, even if you are only a fan of Supernatural and not anime, or vice versa. This is a really good blend of the two and will most likely get you interested in the show or animation style that you don't normally seek out.