^looks like he's wearing a cast shirt.
There are more pics of Vanessa at both sources if you are interested.
eta 2 more from here:
Lucas and his sister twittered about it:
Lucas is there working on The Legend of the Dancing Ninja. He twittered that he is working with Chucky Klapow on choreography. They could legit make an SGU musical with the talent they've got up there right now, lol.
ETA: I'll cook up something for an official birthday post tomorrow but someone twittered at me, suggesting we start trying to get #HappyBirthdayZac trending on twitter. Why not, especially since in some parts of the world it is Zac's birthday already. So breakout another hashtag my friends, lol.