The songs "Katyusha" and "Polyushke Polye" aren't available for the Blu-ray release from Sentai Filmworks, as well as for the Crunchyroll version. Additionally, the credits from the Crunchyroll and Sentai releases are different from the Japanese one. The reason is that the authors obtained the license for the Japanese broadcast free of charge from the original Russian copyright owners, but in the US, the copyright for the song is owned by a different entity, so for Crunchyroll and Sentai Filmworks, it would have to be licensed separately since the original Japanese licensor was unable or unwilling to do that.
Also, the animation was changed for the parts that were deleted in the footage for the Sentai release, plus the subtitles can't be changed in order to prevent reverse-importation. Those parts were deleted altogether for the Crunchyroll version.
Career Resurrection: The role of Saori Takebe was this for Jessica Calvello. She originally was best known as Excel in Excel♥Saga, but doing the character's voice put a ton of strain on her vocal cords (this was exacerbated by ADV ignoring her medical professional's suggestions to give her plenty of rest). After that, she quietly moved to New York, but only could have minor roles over there (her only known major role there was Karin Aoi from DNA²). In late 2013, she moved back to Texas again, returning to major anime roles starting with Girls und Panzer, then landing high-profile roles like Eclair in Fairy Tail The Movie Phoenix Priestess (which was released around the same time as the dub of Girls und Panzer), Kanako Miyame in MariaHolic and Hange Zoe in Attack on Titan (which Jessica was a fan of when it was simulcasted).
TankTeru for Maho, due to her similar role in the series, although Maho is shown to care significantly more for Miho than she lets on.
Tank Sumire for Erika. Both of them are the sidekicks to the main leader of the opposing team, and they both fall prey to attempts by their opponents to hinder them, leaving them unable to fight at full effectiveness. Sturmdere is also a common nickname for her particularly in /a/.
I Knew It: In episode 4, Yukari comments that Miho's former teammates whom she saved when their tank fell in a river must be really grateful for it. Come episode 10 and we see the aforementioned former teammate thanking Miho, and Yukari watching on with a marvelous 'I told you so' expression.
Genevieve Simmons, who plays Noriko Isobe, the leader of Duck Team, as well as Miho's Jerkass mom, Instructor Shiho Nishizumi, as well as a Pravda Member, is the older sister of Juliet Simmons, who plays Rabbit Team gunner Aya Oono.
Newcomer Natalie Rial, who does the voice of Nekonya, as well as several members from the rival schools of Pravda, Saunders, and St. Gloriana, is the younger sister of veteran voice actress Monica Rial, who voices Rabbit Team member Karina.
Recursive Canon: Girls und Panzer draws a lot of influence from "Moeyo! Sensha Gakkou!" (and indeed, the book series' writer is part of the production staff, and the books are constantly referenced in-show). Guess what's included as a limited-edition extra for the fourth Blu-Ray release? A volume of "Moeyo! Sensha Gakkou"... except all about Girl und Panzer's setting.
The Red Stapler: The show put the real Japanese town of Oarai in Ibaraki prefecture on the anime map, seeing an increase in tourism especially after episode 4, which featured the town. For a more specific example, the hotel/restaurant that was shown wrecked by a drifting Matilda got a spike in reservations following the episode.
This  video gives a tour of Oarai, showing the real life version of locations that were used in certain scenes of the anime.
The annual Anglerfish Festival usually draws about 25,000 people to Oarai. On November 17-18, 2012, it drew 65,000 people, because of Girls Und Panzer. Attendance at the 2013 festival was 100,000. Apparently the cast who played the Anglerfish Team all turned out for the event in costume, which presumably helps to account for the boom.
As noted elsewhere, Oarai has turned itself into an anime pilgrimage city, milking the show's popularity for every last Yen. Since the city was devastated by the 2011 tsunami, this has not created any fandom backlash. Comments usually go along the line of 'they really need it'.
Relationship Voice Actor: The English dub seems to be quite a reunion for certain VAs from various Houston-based dubs as evident below:
Two next generation AKB0048 understudies, Kanata Shinonome (Genevieve Simmons) and Mimori Kishida, play Duck Team (The members made up of the Volleyball Club) members Noriko Isobe and Akebi Sasaki. Also, AKB0048 Successor Minami Takahashi the 5th is the driver Shinobu Kawanishi.
Tomomi "Tomochin" Itano the 11th (Allison Sumrall) commands Rabbit Team as Azusa Sawa.
Tsubasa Katagiri plays Tankery instructor Ami Chouno. She also doubles as Mallard Team's driver, Moyoko Gotou.
Megumi Wanaguchi (Meaghan Avocado) is Yuzu Koyama, the Student Council's Vice President and driver of Turtle Team (which consisted of the Student Council members).
Chieri Sono leads Saunders College High's Tankery team as Kei, while Orine Aida is Saunders' cheating third in command, Arisa.
Excel♥Saga: Excel is Saori Takebe, the radio operator for Anglerfish Team, while Hyatt is Karina, the driver for Rabbit Team (they also would go on to be in MariaHolic, about one year later as Kanako and Mariya).
It's all because someone didn't do his job, it's causing everyone to be at a loss. I will never forget that person's name.
As a result, instead of ending around Christmas Eve 2012 as it was supposed to, the airing of the final episode was in doubt. All the production team could promise at the time was that an announcement will be given at the end of episode 11. One station had announced they will broadcast Episode 12 on January 9th.
Yet another minor slip happens later on, with the Blu-ray disc release moved a month to February, meaning the release of the second OVA/disc-only special was delayed as well.
Happened a third time, to the dismay of watchers, with news that Episode 10 might not be ready in time (and as such would have to be aired unpolished), and that Episode 11's airing will be pushed back further, with episode 10.5 shown instead in its timeslot. The official announcement also mentioned that the final two episodes will be aired in March 2013 instead, almost three whole months after the show should have ended.
Troubled Production: It says a lot that a 12-episode series like this has to resort to airing two recap episodes to buy time (again, it bears mentioning that such episodes are usually used as Blu-Ray or DVD extras, and never shown during TV airings), where many multi-cour shows rarely do more than one. Not only that, but the airing of the final two episodes were pushed back three months to March 2013.
What Could Have Been: In the 6th OVA, when Duck Team does it's Hidden Talents sketch of impressions, originally, they had the voice actors for Momo (Kendall McClellan, Darjeeling (Kara Greenberg), Orange Pekoe (Ally Piotrowski), Miho (Margaret Mc Donald), Saori (Jessica Calvello), Hana (Caitlynn French), and Yukari (Rebekah Stevens), doing the voices for the Duck Team members when they were doing the impressions, before ultimately deciding to just have the actual Duck Team voice actors (Genevieve Simmons, Carli Mosier, Cynthia Martinez and Kalin Coates) just voice their characters doing impressions of the other cast members. This alternate take was included as a bonus feature on the Sentai Filmworks Blu-Ray and DVD release of the OVAs.