"Iron Sky", a B-movie spoof drawing the crowds at the 11-day event in the German capital, imagines that Hitler's surviving henchmen set up a lunar colony after the fall of the regime in 1945, biding their time to strike back.

The opportunity comes in 2018 when a US astronaut exploring the dark side of the moon comes face to face with a Nazi soldier clad in a black uniform and a breathing mask.

Behind him, a secret military base shaped like a swastika looms into view, prompting giggles from the packed audience.

The intergalactic farce produced mainly in Finland pits the would-be Fourth Reich against an America led by a Sarah Palin double, who is seen incessantly jogging in the Oval Office.

"This basically came from a stupid joke dreamed up after a trip to the sauna," said director Timo Vuorensola, who generated much of the financing for the film among fans online.