The original series is twenty-seven episodes long, or - minus the openings and endings - around about nine hours. Gurren-hen follows the events of the first thirteen episodes and so is just over two hours shorter than its source material. As you would expect, much of the development is glossed over and the story proceeds at a lightning pace. The story itself is more or less the same as in the series - much of humanity lives underground until Simon and his 'bro' Kamina break free, to find the surface inhabited by 'Beastmen' who pilot giant mechas - with a movie-original opening and ending that sets things up nicely for the sequel. The plot comes across as - unsurprisingly - very rushed; the characters are offered little development and during the middle act there is a ridiculous - but unfortunately necessary - montage to progress the story. Developmental issues pave the way for an adequate at best plot.
The animation isn't a huge step up from the series - if different at all - but the opening and the ending deliver some exciting new material. The ending, especially, is a welcomed feat. The new climax is both thrilling and well executed, and will have you eagerly awaiting the next installment. Corners have been cut, however, with the music. The score by Taku Iwasaki from the series returns with no new additions, which causes Gurren-hen - at times - to feel something along the lines of a movie-length recap; something you've already seen before. New inclusions to the soundtrack certainly wouldn't have gone amiss.
The main trio and the prime supporting cast return in Gurren-hen, though most have left their depth and development at home, particularly Rossiu and Kittan. Yoko fans are offered more excessive fan service and Simon - in the new sequences - is particularly prodigious. The lack of development to the cast is massively disappointing, however, and causes Gurren-hen to come across as rather disengaged and retrogressive.
Gurren-hen is an enjoyable movie, urged on by its source material, but is let down by lapses in development. The middle act could have benefited substantially from some new material, acting as a bridge between the beginning and the end, offering the supporting characters alternate introductions and addressing developmental issues, but instead the staff opt to rehash the series to a disjointed, disappointing effect. The new opening and ending sequences are both longer and far more engrossing than expected, however, which offer the movie some value. If you enjoyed the series, you'll get a kick out of the movie, but if you didn't, it's best to avoid Gurren-hen. If you're new to Tengen Toppa Gurren Lagann, the movie isn't worth your time, and may come across as completely incoherent, with many characters remaining a mystery; without motivation and depth, just empty shells.
