This is an interesting question about the meaning of words, in this case, the word prank. Since what we are dealing with here is an Axis II NPD Ill explain it in those terms. Ive mentioned before some of the feature sets of NPD and described how they present. I noted that NPDs have a limited range of emotion and often only feel anger. But there is one other emotion they feel that runs very, very deep and it the hardest to study and diagnose clinically. But if youre familiarity with them is good, you will know about this. I call it comic-lust. This goes to the question about playing jokes on people. When an NPD is forced to live in a civilized society it is a major, major task to stay within boundaries most of us dont even think about. This means that whenever they are in an uncontrolled environment, or can create one without cost to themselves, there is a euphoric release of these constraints. Its like the giddiness and excitement of going out on a first date, or thrill seeking as my grandparents called it, but 1000 times stronger. This is bad Feng Shui. One of the things NPDs value so much is their freedom from these other emotions (when it serves them sadly, they generally never comprehend the magnitude of the good they are missing completely). So self-serving, base, characteristically narcissistic behavior emerges, sometimes explosively on a crime scene, where the sufferer is in an impassioned frenzy, just like that first date 1000 times over, and this includes enjoying the suffering of others. This is the proverbial, tired meme of lack of empathy coming forth violently to give the sufferer the room to let their boundaries fly apart, to let their disorder express without inhibition. And oddly, when this happens, the sufferer can feel an undercurrent of anger as well, anger at those that constrained them (pretty much everyone). So how does all this manifest? This giddiness of a first date mixed with a dab of anger is what I call comic-lust. Comic-lust is experiencing great humor and excitement in the suffering of others.
When a man accused of murdering your daughter invites you over to plead his innocence with you, then surreptitiously guides you over the floor where your daughter is buried, he is getting a sick kick out of this, having you walk on her grave and not knowing it. It is hilarious to him precisely because he knows how painful it would be to you to find out. Its your pain that humors. When a natural born NPD helps a suffering family try to resolve what happened to their missing child, he injects bits of truth in a false narrative in order to tell you to your face they killed your child and to then laugh about that. Because again, they know you would be hurt if you found out. And they cant help it. Like robots they consistently, reliably do this kind of stuff. And once youve been around it a long time, or been very close to it, you pick up on these cues and tells and can see it where the normal population thinks nothing at all. So, a cruel joke or prank might be to tell the public exactly what car JEW left in, and to even describe seeing him drive out of his own driveway, for a sick punch of laughter. And its like lust. It runs deep and powerful and can be felt for days or even years after the fact. Its a strange combination of anger, comedy and lust that makes the true naturals do things like take keepsakes from crime scenes, taunt police, mutilate remains for no reason, etc. And it really gets scary when you realize that almost all of those personality features seen in disorders actually derive of just one core being; comic-lust.
So, on a crime scene, you look for that engineered contrivance that sticks out as conspicuously hurtful to someone, either physically or in an abstract, emotional way, but not in an obvious way, such as by the crime itself. And if it is a prank gone wrong, you look for that same conspicuous harm engineered in some way to be made harmless, but which in the case of the crime presenting, became harmful instead. The asking of ages of the boys was conspicuous comic-lust, even if I assume in this latter narrative Ive reached that this might have actually been a specific request by S2 made of S1. Either way, it has the same origin. Its comic-lust and that is why it makes no sense to you. You dont have even the smallest measure of comic-lust. It is alien to you.
So, finally, back to the word prank. We all know what it means, but what happens when the mark of the con is the object of comic-lust? This is something sadistic and aberrant, but it can still take on all the appearance and manner of a prank. It is the same for all intents and purposes, its just that the design of the prank, when designed by an Axis II, conveys a comic-lust. When designed by any other person, there will be no indication in the evidence of the deliberate, reckless risk of immense suffering of another person for someone elses gratification.