Assemble Insert is a delightful little OVA from the late 80s, complete with goofy villains, and a definitively endearing protagonist. Beginning with the story, it's a simple setup, with an over-the-top themed gang of bank robbers in power armor, a hapless yet passionate special police unit, and a regular girl with special powers and a heart of gold who comes to save the day. The pacing is snappy, pairing well with the general flavor of the comedy throughout, and its various elements manage to come together to make this anime a real pleasure to watch.
The art is even more impressive. Not only does it capture that warmth that often characterizes older titles, it pairs it with a fun flare unique to its own style, especially in the way it handles character designs, specifically the design of the main heroine. Good character design tells you everything you need to know just by looking at them, and that definitely applies in this case. Marin's face betrays an innocent simplicity and a general silliness that makes her a main driver of comedy throughout, while not being too simple so as to rob her of her individuality as a character. The whole cast is quite distinctive, though they follow more closely to various pre-established archetypes like the crazed evil scientist and beleaguered salaryman.
The sound is also great, with a soundtrack that is catchy as hell, supporting lighthearted voice work and sounds of life which add some much-needed depth to various scenes.
The characters constitute this anime's strongest aspect, not for any complexity or maverick writing, but instead as perfect incarnations of feelings they were trying to capture, while still allowing them to feel like more than just puppets. Marin is the best character in the show, and the best example of this principle at work, reflecting her design as an eager, sometimes foolish girl that serves as the centerpiece of the anime and makes the comedy which surrounds her that much funnier by contrast. I'd say the main bad guy, who literally has the last name Demon, serves a similar purpose for the Demon Seed gang, though he doesn't get as much screentime. Overall, Assemble Insert is a fun, lighthearted quasi-parody of various genres popular at the time, including mecha, magical girl, and idol culture. This one is an easy to recommend feel-good romp with a nice dash of 80s flare.