Cliché Storm: As noted on the main page and much like Strike Witches, VO is packed with elements similar to or straight-up lifted from other series. Whether this contributes to or detracts from the show's enjoyability is entirely up to the viewer
Easily Forgiven: Her sad backstory aside, Rei has helped Alone and through that aided them in killing hundreds if not thousands of humans. The military losses alone would have been apalling considering how many airplanes, ships and armored vehicles the Alone have destroyed. And yet she never faces any real consquences for her actions.
The fact that Showing Rei compassion was a critical part of the test on which the continued existence of the universe depended probably helped.
Fridge Logic: In the final two episodes, we learn that the crow never intended to give humanity a fair chance and plans to destroy the earth anyway and then betray its masters. To do this, it absorbs Rei's remaining four arrows to gain enormous power. So... if this was its plan all along, why didn't it just eat all of Rei's arrows at the very start of the series? If four arrows made it practically unto a god, ten arrows would have likely made it unstoppable even for a full Vivid team, and at best only VividBlue would have been around to oppose it.
It probably wasn't the Crow's plan all along. It said that it led many worlds to their destruction so far, it's most likely that it believed that our world would be no different from the previous ones. When humanity deviated from the script though the Crow decided that because previous worlds failed it is the will of Them for all worlds to fail and so betrayed her original task by devouring Rei. Once it fused with Rei it got Drunk with Power and decided to usurp it's Masters and proclaim itself the Master of the Universes. As an Unreliable Expositor, though, it's best to take what the Crow says with a grain of salt.
Hilarious in Hindsight: Rei, being not only an expy of Homura, but an antagonist for a good chunk of the series becomes funnier when you take into account that Homura became an antagonist herself a couple of years later.
Episode 6 has such things as Himawari and Akane touching each other and Wakaba scooping up Himawari in a Bridal Carry.
Wakaba and Himawari continue to act like a couple throughout the series, often holding hands and spending a lot of time alone together.
Episode 8 gives us little gems like Wakaba hugging Himawari while the girls see Akane before she's rushed to the emergency room, and the two of them wearing matching green and yellow clothes.
Episode 9 takes the Himawari x Wakaba ship to a whole new level. It starts off with Wakaba cleaning Himawari's apartment like a housewife. Then she makes her go out with her in a cute dress. The barettes that Wakaba gave to Himawari turn out to be her most treasured possessions. Then the ending tops the entire episode with Himawari setting up every Sunday for the next year to be spent with Wakaba.
Nausea Fuel: Mayonnaise is Akane's Trademark Favorite Food, which she slathers on everything she eats, and when she gets the other girls to try it, they like it. How can Akane eat practically anything with salty, eggy and tangy tasting mayo? It's because it's not actually that kind of mayo. Japanese mayonnaise has a much different and sweeter taste than regular mayo. It's a popular condiment in Japan and it's put on a wide variety of food stuffs that people wouldn't even try putting regular mayo on. Not knowing that means you're likely to go through Akane's mayo scenes feeling a little queasy, especially in episode 10 where it explodes over an entire room.
Nightmare Fuel: The crow SWALLOWING REI WHOLE might count for this, due to how it comes straight out of nowhere.
Tear Jerker: Rei talking with Akane about how she wants and needs to be friends with her and the other Vivid girls, while simultaneously thinking about how she wants to kill them, without realizing that they're the same people.
What An Idiot: Kenjiro making the entire docking system dependent on Akane. When Akane is put in the hospital, the other girls have no way of forming any of the Vivid forms, and they nearly lose a battle as a result. It's implied that there's some sort of reason why the system is designed this way, but it's never properly acknowledged or explained.