The fourth season of That '70s Show arrived on DVD four years after it was shot and broadcast, giving director David Trainer enough distance to make some nice and helpful analytical observations across his commentary track on "Eric's Depression." The first of three episodes with a commentary, it's ideal for this purpose, showcasing all of the essential attributes of the series in just about their optimal states at this stage of the series' development; it's also damned funny. The other commentaries, on "Class Picture" and "Hyde's Birthday," are just as rewarding. The other bonuses include a superb four-minute montage of the entire season's highlights, plus a string of onscreen featurettes devoted to David Trainer discussing eight years of work and how everyone keeps their edge professionally across that time; there are also what are called "'70s flashbacks" devoted to actresses Laura Prepon and Mila Kunis, presenting their thoughts on the series and its role in their lives, intercutting personal and professional recollections with relevant scenes in the series. The transfers for the episodes themselves are state-of-the-art, and the full-screen (1.33:1) images are gorgeous. Each show has been given five chapters, delineating the natural breaks in the episodes for credits, commercials, etc. Each disc opens automatically to an easy-to-use menu that offers simple access across two layers to all of the bonus materials and individual shows. The audio has been mastered nice and loud as well.