These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Sanya's popularity is vastly disproportionate to the amount of screen-time she gets. And she was one of the first characters to receive a figurine.
While The Movie cameos basically every Japanese fandom favorite they can cram in, Heidimarie in particular is given the third most significant plot driven scenes after Shizuka and Yoshika, and is basically treated as a member of the 501st (read: primary cast) at the end, in all but name.
Fetish Retardant: If you're not into the series' particularbrand of fanservice, the panty shots and such can come off as this. This has turned some viewers off the series completely, while others put up with the fanservice for the sake of the entertaining plot and likeable characters.
Fan-Preferred Couple: Perrine and Lucchini. Many of their interactions are rather amusing in terms that they're complete polar opposites, especially episode 9 of the second season, where they share tons of Ship Tease moments, which would lead the popularity of this couple.
The pictures on the left are, as far as I remember, actually Wochenschau footage, explaining the Blitzkrieg tactic to the german populace, with the tip being the assault force, and the rest assembles a secure line of defence for the convoys that supply the tip to keep it going. Yes, this does not make it better, I am clear on that.
Speaking of pants, any discussion of the series on Youtube will inevitably contain jokes about how pants have been outlawed/were never invented/are unnecessary because the main characters are just that badass/ect.
Moe Moe: Most characters, but especially Sanya (the creators seem determined to play her cuteness for all its worth) and Lynette (clumsy, shy, low self esteem...we could go on).
Stoic Woobie: Mio. The final episodes of Seasons 1 and 2 deal with her losing her magical power, and by extension, her ability to fight the Neuroi. Every aspect of Mio's character screams "Don't You Dare Pity Me!," but just try to watch her break down in tears in the face of losing her way of life and place in the 501st and not feel sorry for her. Fortunately, she comes to terms with it.
Tear Jerker: Happens a few times in season 1. Most notably near the end of "We're The Same".