This OVA is just a small set of recycled scenes from the original series, along with a few new ones where the first 1-2 minutes of the 1st episode are re-made in different scenarios (like everyone being an alien). It's boring and unoriginal, something to skip, but that's not where my very bad score came from:
For those who didn't notice, Sakamoto desu ga? Ends with indications of Sakamoto being sick and near death, it's easy to miss but there's a few dialogues indicating that he's been to the school nurse's office frequently or things that allude to him being constantly sick, also in the end Hayabusa points out that Sakamoto is lying about his NASA internship and Sakamoto doesn't even bother denying it, Hayabusa is onto Sakamoto's lie and asks if he's leaving with any regrets. You can google it, there's things like reddit threads with very good explanations, the main evidence for me is the last chapter's cover art where Sakamoto is seen in a school locker as if in a casket, with his arms crossed, this points to his imminent death.
This is what made Sakamoto desu ga? Be all the more significant, it's not only a comedy but there's a big subversion of expectations that gives a deeper meaning to an otherwise silly story, it doesn't make it a masterpiece but it's a great element in the plot. That's why I give this OVA a 2, it is indicated in the OVA (through breaking the 4th wall) that the studio decided to make this because they didn't fill their 13 episode quota and only reached 12 so they're making the OVA hastily, this is not something coming from the original source, and it shows because they depict Sakamoto feeding birds in the US, meaning that he wasn't sick and went to NASA, this goes against the canon. Along with the disgusting lack of effort that makes this OVA unwatchable, this lack of attention to the story is what makes the OVA horrible.