Katniss gives Prim the Mockingjay pin that will keep her safe, no matter what. This is way different from in the books, where Madge Undersee gives Katniss the pin.
A slightly different look at the selection ceremony in District 12 — President Snow is addressing the people of the district, via a big video screen. "Happy Hunger Games." Heh. The first trailer had a lot of this scene as well, and you can see your screencaps here.