I have a vivid recollection of an action movie where someone pulls the pin out of a grenade (I think in an attempt to commit suicide or something like that) and someone else calmly picks up the pin and puts it back into the grenade. What am I thinking of?
Well, I doubt this is the movie you’re thinking of, but Nicholas Cage did so in The Lord of War, which Himself & I watched over the weekend.
Maybe it was The Rock (is Nic Cage stuck in my head, or what?) but I can’t be sure.
As long as the spoon is not released, the pin can be replaced and the grenade will not explode. When the spoon is released, the fuse ignites and the grenade will explode.
The Delta Force a Chuck Norris “vehicle” I think???
I’m pretty sure there was at least one episode of MAS*H where that happened.
A patient pullled a pin out of a grenade and everyone sang to him while they looked for the pin on the ground. Probably not what you’re looking for, but… well, it could be.
Yeah, but sticking the pin back in is not as easy as it sounds.
The pin is exactly what the name implies: a cotter pin with a ring to make pulling it out easier. Putting it back isn’t any more difficult than putting any cotter pin back in place.
I have a practice grenade on my desk at home. Pin comes out, pin goes back in. No problem.
Are you absolutely sure it’s a practice grenade? 
Sure - NOW it does, after you’ve weakened the sprimng and widened the hole through repetition. Try it with a granade fresh from the box.
Joe Friday did that once when he and Gannon wrestled a grenade away from a suicide bomber on the 1967 Dragnet series.
I have. It was like putting any other cotter pin back in place. The pin was slightly sprung and had to be squeezed together to fit back through the hole. It wasn’t particularly difficult. The pin has to fit through the hole during initial assembly of the fuse mechanism and they don’t fit so tightly that something like a hydraulic press is necessary for the process.
There’s a joke in here somewhere. (In Scumpup’s version, not quite so much.) 
It was Lord Of War, thanks!
And I’d tend to trust the Israeli about the topic of grenades, by the way.
Why does his nationality give him special expertise on grenades?
Heck yeah. They eat them for breakfast over there!
He’s also a veteran of an army that takes such training seriously.
Oh, I see. Apparently other armies, like the one of which I was a part, treat grenade training as more of a lark.
For what it’s worth, I’m with you on this one. The physical effort to replace a pin is negligible. On the other hand, if you’re handling a live grenade, adrenaline rush could cause you some problems hitting the hole.