@Stahesh need English subtitles to get the set up to the joke
@sardonicsmile He started with some harmless cheers and lulled them in until they just reacted.
More complex answer: The people in the audience were maybe between 30 and 50. Most of them grew up, went to school during Hitler's regime. It took along time for the germans not only to overcome the reflexes they learned, when they were very young, but also to deal with the horrors and the guilt.
@sardonicsmile When this clip was shot, one of the german countries, Baden-Wuerttemberg, had a prime minister who was a military judge during the war and sentenced soldiers to death even after the war was over.
After Sieg Heil he goes on: That cannot be for real! So many old comrades are here tonight?!
@sardonicsmile Zicke Zacke Zicke Zacke Hoi hoi hoi - a German battle cry/drinking cheer made popular in the US by "The Fox" Bill Foster from the Man Show http://de.wikipedia.org/wiki/Zicke_zacke_zicke_zacke_hoi_hoi_hoi
There talk about it. https://www.reddit.com/r/videos/comments/18s7wd/german_comedian_tricks_audition_into_shouting/