A very professional and dedicate actor for his age. He's the same as age as me, only 19, yet he is already so mature.
I watched some interviews and clips of him and it seems like Alexander Ludwig is a very true and fun person to hang out with. He doesn't ignore or pretend to not hear a question from people on the streets, he's not rude to them too, he's very polite and keeps it casual.
He respects and care for his fans a lot, at least from what I can see. He moves like a ninja when his fans asked for his autograph or picture, I don't see many celebrities that are so passionate about it. He could just simply say "I'm sorry but I have to go" and get it over with but he didn't.
I've watched 2 of his previous films when he was younger (and a lot smaller in build) - The Seeker: The Dark Is Rising and Race to Witch Mountain. I think those films are great stepping stones for him in the blockbuster The Hunger Games.
A pity though, he died at the end of The Hunger Games, meaning we won't see him in Catching Fire or Mockingjay anymore. Lucky if there's a flashback of some sort when they visit District 2. I admire his determination and passion.
As I said earlier, he was still very skinny and not as big as he is as Cato. In some interviews he said he had to put on 40 pounds for the role, just because he wanted people to feel intimidated by Cato's physical size and strength. It's not stated whether if the director of The Hunger Games, Gary Ross, specifically asked him to. But anyway I still think it's a pretty huge sacrifice he made for the film.
Before The Hunger Games, I think he's pretty underrated. Now almost everyone recognized him as Cato, which I think it's his breakout time and his hard work has finally paid off.
Fun fact: Not only is Alexander Ludwig an actor, he's a singer and has just released his debut single. If that's not enough to impress you, he's also the model for Abercrombie & Fitch!
Interview 1: http://www.youtube.com/watch?v=AXEH1ZMH1qs
Interview 2: http://www.youtube.com/watch?v=ovFEQIj4kuA
His song: http://www.youtube.com/watch?v=nFNdqPNAMfs
His A&F photoshoot: http://alexander-ludwig.us/2011/04/21/alexander-ludwig-abercrombie-fitch/