1) Facebook is blue because Zuckerberg is color-blind: According to a 2010 profile from the New Yorker, Facebook’s main color is blue because Zuckerberg has a red-green color blindness. In the interview, he told reporter Jose Antonio Vargas that “blue is the richest color for me — I can see all of blue.”

2) He says he’s not that interested in money: This is a well-known fact, but one that continues to surprise. In several interviews and goals statements, Zuckerberg has made it clear that making money is not his first aim — connecting the world is.

“Simply put: we don’t build services to make money; we make money to build better services,” Zuckerberg wrote in the company’s S-1 filing to go public.

3) He’s a fan of Taylor Swift: Yep. Says so on his Facebook profile.

4) He’s spent a year trying to only eat meat that he kills: Zuckerberg sets annual challenges for himself, and the challenge for 2011 was to move toward vegetarianism and only eat meat that he killed himself.

“The reason for this is that I feel lucky for having such a great life. I like eating meat and before this year I ate it almost every day,” he wrote. “In order to practice thankfulness, I want to be more connected to the food I eat and the animals that give their lives so I can eat them.”

5) He designed his wife’s wedding ring: Zuckerberg was the one who designed wife Priscilla Chan’s wedding ring, which is a ruby flanked on either side by diamonds. The ring has been a strange target of criticism, with the Daily Mail criticizing the gem’s size and saying that it’s not nearly the rock that one would expect of a billionaire.

6) He loves his dog: Okay, maybe this isn’t surprising, but it is an important fact about Zuckerberg, if his Facebook page is any indication. Beast Zuckerberg is a Puli, or a type of Hungarian sheepdog, and is the subject of several of Zuckerberg’s and Chan’s Facebook posts. He helped walk Chan down the aisle and even has his own page — on which he “says” he likes “cuddling and herding things.”

7) Zuckerberg’s many nicknames: To friends, he’s Zuck, but according to a 2010 report from CNN, his mom has her own special name for him: Princely.

The report also rounded up this tidbit from Harvard classmate Rebecca Davis O’Brien: Zuckerberg’s nickname after joining his fraternity Alpha Epsilon Pi was “Slayer.”

8) He once wore a tie every day for a whole year: Another one of his annual challenges that may surprise you: Zuckerberg once wore a tie every day for a year. That’s likely a surprise to anyone who knows that he normally wears a hoodie, jeans and sneakers — even when others think he shouldn’t.

But he went more formal for a year and outlined his reasons on his Facebook wall: “My 2009 challenge was to wear a tie for a whole year. After the start of the recession in 2008, I wanted to signal to everyone at Facebook that this was a serious year for us. Great companies thrive by investing more heavily while everyone else is cutting back during a recession. But great companies also make sure they're financially strong and sustainable. My tie was the symbol of how serious and important a year this was, and I wore it every day to show this.”

9) He really liked Andy Samberg’s impression of him on SNL: Zuckerberg is a figure of a lot of gentle (and not-so-gentle) ridicule in the media, but he particularly like the treatment he got on Saturday Night Live.

“Andy Samberg plays me on SNL. I'm a big Andy Samberg fan so I thought this was funny,” Zuckerberg wrote on his Facebook Timeline. Samberg later reprised his Zuck impression for f8, the social network’s developer conference.

10) He once built a program called ZuckNet, just for his family: Again from the New Yorker profile, Zuckerberg once built a program for his dad, Edward, who needed a quick messaging system for his dental office, and for the family home. It was, essentially, an early version of AOL’s Instant Messenger.

“The receptionist used it to ping Edward, and the kids used it to ping each other,” the report said.