On the second day of shooting Matthias Schweighoefer and Friederich Mücke had to laugh for more than 3 hours and couldn't hold on so that production had to stop. After Lunchbreak they continued to laugh so much that an other scene which supossed to be shot on the same day could not wrapped.
Camera Operator Stephen Drinon asked Schweighöfer and Mücke why they do not do push up's before their takes ? Because both were topless in a lot of scenes. They asked him why should they ? Drinon told them when he was shooting independence day Will Smith were doing push up's before takes to make him look more muscled. After that they start doing push up's.