When the Last Battalion and the Millenium airships enter English territory, the Major triumphantly declares that "finally, the sea lion has crossed the ocean and is heading up the hill". This is a reference to Operation Sea Lion, the Third Reich's planned invasion of England.
The final animated TV series to get an R18+ rating from the Australian Classification Board for reasons other than sexual content (the rating was instead given for gory violence) and would remain that way until a few years later when Netflix's Trailer Park Boys: The Animated Series (2019) received it for coarse language.
Volumes One through Four were released in two versions in North America: a single disc edition that included just the OVA itself, or a two-disc edition that came inside a Steelbook with a extra disc with bonus features.
Volumes Five through Ten were released only in a DVD/Blu-ray combo pack in North America.
All the English voice actors from Hellsing (2001) were brought back to reprise their roles except Michael Marr (Sir Islands), who was replaced by Doug Stone.