Invalidation Is About Domination

Invalidation is a domination and bully tool.
Their desire to make a target into a "lower status" person is so great that a Narcissist will literally invalidate ANYTHING about the target, including things that have nothing to do with "status" in the real world. When they act like a target is "making up stories" when they mention that their first cousin is Will Smith, that's almost understandable (almost); most people would be a little skeptical about such a claim (although non-narcissists would not accuse the person of lying, they'd at least suspend belief at first).

However a Narcissist will invalidate ANYTHING that a target says, and talks about. ANYTHING. And sometimes it's to the point of ridiculousness.
So if a target says they went for a walk and saw a deer, the Narcissist might respond as if they believe them, but also might act like they're "just saying that to get attention".
(Yes, that's right, claims to have seen a deer on a walk just sounds CRAZY! and since it's so OUTLANDISH, it would of course ONLY BE SAID if the person was "TRYING TO GET ATTENTION"... you watch, soon the Local News Channel will pull up out front and want to interview the person about their first-hand-account of witnessing a deer on a walk...)

Invalidating anything and everything about a target can become a habitual reaction to the target's every move and word, and it serves to constantly give the impression to EVERYONE, including the target, that the target is completely self-centered, attention-seeking, grandiose, a liar, a story-teller, a and even delusional.

Since of course the target is going to defend themselves when they get made out to be a "liar" or "attention seeking" (if they're at all healthy~), the Narcissist will use THIS TOO as ammunition against the target, claiming that they're "argumentative", "hostile", again "delusional", "always have to be RIGHT", and even "abusive". 

Unfortunately, VERY FEW people witnessing this have enough self-awareness to see this behavior for what it is, even when it's going on all the time. Also, since many people are closet bullies themselves, they go along with it and don't want to expose the game, since they're playing it too.

There are a LOT of game-players in the human species who live through their envy, insecurity, and desire for superiority and special privilege, who will go along with targeting another human being. Especially if they have jealousy toward the target, or if the target has or does something they envy. 

A Narcissist will invalidate anything AT ALL about a target person, even if there is blatant, obvious evidence that something is true. A person could be in a hospital bed, in traction, with their mouth covered in a plaster cast, and the Narcissist would imply that the person is "making a big deal out of it" or "trying to get attention".
It's NOT ABOUT "reality", it's about their desire to make the target themselves "invalid", and therefore a very "low status" person, an "unliked" or "unwanted" person, or a "non-person", someone who isn't a valid member of the group, the family, the community, or even the partnership.

Invalidation behavior is also a part of "Gaslighting".