Very cryptic reference: Alice's CV voices Suzumiya Haruhi, and her boyfriend is called Takashi. It's a nod to Takayuki Narumi whom Suzumiya Haruka is in love with.
, the real-world Õarai city's masked superhero avatar.
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 [1] 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
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'.