Black US astronaut James Washington, on a mission to boost the flagging electoral fortunes of a US president clearly modelled on Sarah Palin, stumbles across the huge Swastika-shaped complex and is captured.
His madcap adventures, set in 2018, see his skin turned white by an Albert Einstein look alike, send him back to Earth where he is greeted as a lunatic and finally to the moon again to try to save the day, and his skin.
The movie has its official world premiere at the Berlin film festival where it screened out of competition on Saturday.
Amidst a typically dark and gritty selection of films at this year's festival, Iron Sky has been among the most talked about by the thousands of journalists covering the event.
Producer Tero Kaukomaa said a large part of the funding came from "crowd-sourcing" either on the Internet or through selling merchandise to fans.
Of the 7.5 million euro ($9.89 million) budget, almost 1million was raised that way, he said, in turn helping to bring more mainstream investors on board.
Director Timo Vuorensola said the original idea for the oddball plotline was born in a Finnish sauna "as all good things from Finland usually are".
He also directed the 2005 picture "Star Wreck: In the Pirkinning", another sci-fi comedy funded by fans which went onto become a cult hit.
German producer Oliver Damian admitted there had been some resistance within Germany to making a film that made light of the Nazis.
"Over the years we needed to organise financing and we had a lot of obstacles to overcome in Germany because a lot of people were very critical of the project," he told reporters after a packed press screening.
"We (younger Germans) have a different past and we are fully aware of this. I think you can make a dark comedy (about Nazis). "The film is supposed to be fun. This is important. At the end of the day we found funding partners in Germany and the film will be released here in April so we found people who believed in the project here as well."
Actor Christopher Kirby, who plays Washington, did not believe it was a genuine script when he was first approached to consider the part. He stars alongside Julia Dietze, who portrays the Nazi ideologue Renate Richter.
Together, the two characters become involved in a life-or-death mission to halt the Nazi onslaught, in particular its secret weapon, the massive Gotterdammerung spaceship.
Meanwhile on Earth, the US president sees an opportunity to stay in the White House for another term.
"It's wonderful," she crows. "I'm a war-time president. I thought I was going to have to bomb Australia or something."
Her response is to dispatch her own secret weapon, the USS George W. Bush spaceship. (Reuters)
