Is it normal for narcissists to show up “casually late”?

I think trying to equate the punctuality of a person on a random occasion to a personality disorder is beyond retarded.

I'm not really sure how to answer that. People with narcissistic personality disorder (NPD) have quite a few warning signs such as

- Grandiose sense of self-importance believing that they’re better than everyone else and expect recognition as such—even when they’ve done nothing to earn it. They will often exaggerate or outright lie about their achievements and talents. And when they talk about work or relationships, all you’ll hear is how much they contribute, how great they are, and how lucky people are to have them in their lives.

- Living in a fantasy world that supports their delusions of self-importance that if threatened will be met with rage and extreme defensiveness and should be handled with caution

- Needs constant praise and admiration. they'll surround themselves with people who are willing to cater to their obsessive craving for affirmation. These relationships are very one-sided. It’s all about what the admirer can do for the narcissist, never the other way around. And if there is ever an interruption or diminishment in the admirer’s attention and praise, the narcissist treats it as a betrayal.

- Sense of entitlement. They will expect those around them to automatically comply with their every wish and whim. That is their only value. If you don’t anticipate and meet their every need, then you’re useless. And if you have the nerve to defy their will or “selfishly” ask for something in return, prepare yourself for aggression, outrage, or the cold shoulder.

- Exploits others without guilt or shame. They lack empathy. In many ways, they view the people in their lives as objects—there to serve their needs. As a consequence, they don’t think twice about taking advantage of others to achieve their own ends. Sometimes this interpersonal exploitation is malicious, but often it is simply oblivious. Narcissists simply don’t think about how their behavior affects others. And if you point it out, they still won’t truly get it. The only thing they understand is their own needs.

Frequently demeans, intimidates, bullies, or belittles others. Narcissists feel threatened whenever they encounter someone who appears to have something they lack—especially those who are confident and popular. They’re also threatened by people who don’t kowtow to them or who challenge them in any way. Their defense mechanism is contempt. They may patronise or dismiss the other person as if to demonstrate how little the other person means to them. Or they may go on the attack with insults, name-calling, bullying, and threats to force the other person back into line.

Ultimately, those with NPD won't give you much of a sign regarding time. Aside from the fact that it would need to be in their interest to actually turn up. That said, that's the same for a lot of people so I wouldn't classify someone as having NPD for that.