The Rambo movie franchise is many things. dark, grim, action-packed, and especially in the case of the latter films, bloody as hell. However, one would never use the term "funny" to describe anything in Rambo movies, unless you had a really twisted sense of humor, but it appears that even in the film's darkest moments, the cast was still able to have some fun.
Sylvester Stallone recently shared an outtake moment from First Blood, the original Rambo movie, which includes Stallone himself along with Richard Crenna, who played Rambo's friend and mentor Colonel Sam Trautman throughout much of the franchise. The scene is dark as hell, as it's John Rambo asking his friend to kill him, but that makes the moment that comes that much more jarring, as the scene breaks down and everybody starts laughing. Check it out.
Sylvester Stallone adds a comment to the clip that he misses "The Colonel." Richard Crenna played the role in the first three Rambo films. Unfortunately, the actor passed away in 2003, and so was unable to reprise the role in the latter two films. Rather than recast Trautman, the decision was made to let The Colonel die as well. It certainly would have been hard to have anybody else fill those shoes.
This particular outtake is interesting because in addition to being unusable because of the laughter, it's also from the film's original ending which was never used. After Rambo has brought the entire small town police force down on his head, Colonel Trautman goes in to try and talk Rambo down. Rambo asks his friend to kill him, Rambo is clearly in pain. As we see in this clip Trautman puts the gun down, but in the next moment of the filmed ending, Rambo grabs Trautman's hands and moves the gun back into position. It immediately goes off, shooting Rambo in the gut. It's unclear exactly who is the one pulling the trigger, Trautman or, more likely, Rambo himself.
The original ending to First Blood, the novel written by David Morrell which the film was based on, is darker still. Trautman kills Rambo, blowing his brains out with a shotgun, just before Rambo kills himself, and likely others, in an explosion of dynamite.
In the version of First Blood that was released, Trautman talks Rambo down and gets him to give himself up. Whether intentional or not, this ending allowed something none of the others would have, sequels.
The sequels would go on to be much more traditional action movies than the more character driven First Blood. The most recent film in the franchise, Rambo: Last Blood, came out in 2019. Despite the title, the possibility of future Rambo movies is out there, and while Last Blood was no box office smash, by virtue of its relatively small budget, it wasn't a bomb either, so a sequel could happen.
It probably won't be very funny, though.
