Answer: Painting himself up and going trick or treating naked in Vietnam.
Step-by-step explanation:
Curt Lemon according to the text just loved acting overly macho. He would engage in stunts that he did not have to just to prove his manliness. On one particular night bring Halloween, he went trick or treating to Vietnamese houses naked and painted up.
This was a particularly dangerous stint because Vietnam was a war zone. They were in an actual war. To go out without gear in a country where you could easily be considered hostile without any gear to protect you can lead to death. This is what made the stunt dangerous.