In District 11, when the soldiers open up their expandable batons after the salute, the batons of the two soldiers at the end do not open. The 2nd soldier from the end tries to hide his baton behind him.
It was previously mentioned that Johanna talks to Katniss backstage between their interviews with Caesar when no other Tributes had left the stage after their interviews. However, this explains why Johanna is not in any of the shots while both Katniss and Peeta are being interviewed, but is back on stage after Peeta reveals that Katniss is pregnant. Johanna had gone backstage to fix her dress.
When the Quarter Quell is announced, a wide shows Katniss, Prim, and her mother on the couch. Her mother is shaking her crossed legs, and Prim is petting her cat Buttercup. In the next shot, Katniss's mother's legs are apart and still, and Buttercup is gone.
After the jabberjay hour where only Katniss and Finnick are tortured, Johanna says, "Your fiancé is right". Either Johanna somehow knows for a fact that they did not get married in secret - unlikely - or she should have actually said "Your husband is right", since Peeta had told Caesar in the interviews that he and Katniss had gotten married in secret.
In District 11 an elderly man is dragged from the crowd to the steps of the building and shot in the head. We see that he has no crutch but after Katniss looks down on the scene when his body is taken away, there's a crutch near where his body fell.
When Katniss pulls a wire from the lightning-struck tree down toward the beach, the wire gets stuck further up the hill. That shouldn't affect her ability to keep moving because she is holding the coil.
Peeta opens an oyster, finds a pearl, and gives it to Katniss. The inside of the oyster shell is very white, but the pearl is dark gray. Pearl-producing mollusks create pearls that are the same color as the inside of the shell. Oysters with white interiors produce only white pearls.
If you listen, you can hear Johanna angrily stomping off the stage after she curses everyone out. During Katniss' entire interview (after seeing her backstage) Johanna is absent, only 22 people are seen up there. She doesn't appear until Peeta's interview where she can be seen at the far left.
After Peeta is offered the drink that will make him vomit, he is warned not to do it there because he will vomit on the floor. When Peeta turns away, the person Peeta gave his glass to is shown drinking from it. Yet Peeta isn't warned not to drink it, he is being offered it because it will make him sick and able to eat more. The man drinks it because he wants to vomit so that he can eat some more.
Statistically, it would be almost impossible for all 12 districts to have a living male and female past victor to compete in the 75th Hunger Games. In the previous film The Hunger Games, Haymitch mentioned that "Career Tributes" from Districts One and Two won the Games almost every year. Even if just over half of the past Games were won by Career Tributes, subtracting previously identified victors leaves 30 past victors to be distributed as one male and one female from each of the 10 remaining districts. That also assumes that none of the victors have died of old age.
It is hinted that the 3rd Quarter Quell idea, of reaping tributes from existing victors, is from Plutarch. But in the end he is revealed to be the leader of the rebellion, hence his idea to have Katniss survive the game and be the Mockingjay seems irrelevant since the arena is a constant-dangerous arena. (Although in the novel, the 3rd Quarter Quell reaping idea wasn't of Plutarch since he says that "I never dreamed you'd (Katniss) be a tribute (in the game) again").