I have spent entirely too much time thinking about Mark Zuckerberg's outfit at his birthday party

• Mark Zuckerberg had a 40th birthday party, which looked like a great time.
• But I noticed he had a slight outfit change in his photos. I was determined to find out why.
• Yes, I am aware there are better things I could do with my life.

The Instagram photos from Mark Zuckerberg's 40th birthday party left me with many questions. Questions that I am prepared to investigate using my skills not just as a journalist but also as someone who has attended a lot of parties.

Let's start with the basic facts. The family-friendly party was thrown by Zuck's wife, Priscilla Chan, and featured a bunch of miniature replicas of meaningful places in his life (his childhood bedroom, his dorm room, early Facebook offices, his first apartment, and his favorite pizza shop in Harvard Square). Cute!

When the Meta CEO posted photos of the party on his Instagram profile, people immediately noticed his outfit and how he was going all in on his new swag style with his gold chain and shirt. Now, typically, I don't like to spend too many of my precious few brain cells thinking about Mark Zuckerberg's personal appearance; it feels a little too circus and no bread. But this was different.

Something in these Instagram photos was amiss.

In two of the photos, he's wearing a slightly different outfit: The gold chain is missing, and his T-shirt is plain black.

Let's start with the shirt, which says "Carthago delenda est," Latin for "Carthage must be destroyed." (My colleague Kieran has more info on the context of the phrase.)

Zuckerberg is known to be a Roman-history fan (his daughters are named after Roman emperors). But is he such a fan of Roman history that he goes around wearing T-shirts with his favorite Latin slogans?

He's been really into fashion lately, so perhaps the shirt is some fancy designer shirt that's low-key $200?

Or, another option, which is my theory: He didn't choose the shirt; the shirt was gifted to him during the party.

Looking for clues in Zuck's party outfit

Let's examine the evidence.

The first notable thing is that one of the miniature room sets is of the Facebook office during the 2016 "lockdown," when the team was working hard to compete with Google+ (lol). During that time, Zuckerberg tried to inspire his troops by using that phrase from the Roman senator Cato — "Carthage must be destroyed." According to a book by a former employee, there were posters with that phrase around the office during that time. So we know that this phrase is very connected to one of these miniature rooms, specifically.

Perhaps the shirt was given to him inside the miniature room that was a replica of Facebook's "lockdown" phase, as a nod to that phase of his life.

This would explain why the shirt seems ill-fitting. Note here it seems billowy and wide. Zuckerberg typically wears a more fitted T-shirt.

And here, you can see that the sleeve of the shirt seems very crisp — as if it were a shirt worn for the first time with the fold lines on it.

We've all had the experience of showing up at some event — a fun run or company picnic or whatever — and being given a shirt with some screen-printed logo on it to wear over your regular shirt. This has all the trappings of that.

So one theory is that Zuck wore a plain black tee to his party — the one you can see in two of the photos — and then, at some point, was gifted the Carthage tee as a surprise and changed into it for the rest of the party.

Now a quick note about the chain necklace: I believe the explanation for the necklace is that it was also gifted to him during the party, along with the Carthage shirt. The chain necklace is something of a meme after digitally altered photos of Zuck in a chain with a beard went viral.

We get some more details about this party from Chan's Instagram profile. Her caption says, "Mark doesn't usually let me go big for his birthday but for his 40th I was allowed to throw a bash as long as our friends and family also roasted him."

AHA! So we know that this was also a ROAST — more fodder for the theory that the shirt and chain were gifted during the party as a form of light roasting.

Chan's outfit also gives us a clue. She's usually very stylish, but for this party, she's wearing jeans, white sneakers, a boxy white T-shirt, and two gold chains. My theory is that this wasn't just her regular, casual party attire — she was dressing up in a typical Mark outfit as a joke, chain and all.

Other attendees also seemed to wear some version of a Zuck costume. For example, Bill Gates is wearing basketball shorts and a hoodie sweatshirt.

Joel Kaplan, Meta's head of public policy, appears in one of Chan's photos holding a mic to potentially roast Zuck. Kaplan appears to be wearing some heinous form of athletic wear, presumably a tribute to his boss' interest in MMA.

All of this goes along with a clear theory:

Mark showed up to his party in a plain black shirt and no chain. During the course of the party, he was gifted a chain and a "Carthage must be destroyed" shirt as joking references to his past and present.

There are still some things this theory doesn't explain, like the fact that the T-shirt seems to have some sort of reversible blue-and-white-striped lining.

The lining suggests the garment is a higher quality than a simple Gildan or Hanes tee — perhaps it is an expensive designer shirt after all. (A rep for Zuckerberg did not respond to questions about the outfit.)

Between the lined shirt and Gates' unholy basketball shorts (I'm pretty sure they're these Nike ones, by the way), there are some mysteries that I just can't solve. But I feel confident in my assessment that Zuckerberg's outfit was gifted to him as a joke during his party.

I also am confident in my self-assessment that I need to find much better things to fill the void in my life than thinking too hard about what Mark Zuckerberg is wearing.