Ben Stiller as a movie “tough guy” is your first clue....
That's what I was thinking. Rambo Stiller.
The whole scene looks fake too. Looks like they filmed it along the highway, just down the street from the Kukui Grove mall in Kauai. After they were done for the day heck they could just dart across traffic and head for the Starbucks.
With Jack Black watching their back.
Stiller, Downey, and Black play actors who are filming a war movie in Vietnam when they stumble into the middle of a real drug war, but they think they are still filming the movie and there are hidden cameras everywhere.
What ruins it for me is the fact that Tom Cruise is also staring in it.