Annie and Finnick Odair's son was born after his father Finnick's death. He was conceived shortly after Finnick and Annie's wedding; therefore, Annie was pregnant when Finnick left to fight against the Capitol for the Second Rebellion.
Finnick, for his part, never knew that Annie was pregnant in the first place, and all we see of the boy is when Annie sends Katniss and Peeta a picture of their son, and they put it in their memory book. The boy, although never named, was raised in District 4.
Shortly after, we see that the tribute accompanying him from District 4, his former mentor Mags (the late Lynn Cohen), volunteered to protect him and Annie Cresta (Stef Dawson) — the love of Finnick's life.
Johanna and Finnick were friends prior to the 75th Hunger Games, most likely having formed a bond during previous Hunger Games where they were mentors. They were allied during the 75th Games, along with Wiress, Beetee, Katniss, Peeta, Blight, and Mags.
Chia Mags kisses Finnick on the mouth to briefly let him know that this is the last time she will see him. It's her way of saying "Goodbye" but in a more affectionate way.
While the Hunger Games film never talked about it, the Catching Fire novel explained why she could only communicate through hand gestures. Katniss briefly mentioned that a previous stroke could have caused Mags' garbled speech. However, post-traumatic stress disorder could have also caused her speech incapacity.
The female Morphling, however, appears almost coincidentally, and Peeta even mentions that they don't know her real name. Given that she is willing to make the ultimate sacrifice to protect Peeta, it's safe to assume that the Morphling was committed to the rebel cause.
In a way, Finnick has outsmarted Katniss here by saving Peeta's life. Now Katniss "will never stop owing Finnick." He's done her the kind of favor she can't easily pay back; now she can't let him down.
Also, Mags was Finnick's mentor, and most likely helped mentor Annie. They would have all lived together in the District 4 Victors' Village. Much like how Katniss, Peeta, and Haymitch became family, it is probable Mags, Annie, and Finnick did as well, so Mags may have felt a maternal kinship towards the younger two.
Johanna won the 71st Hunger Games by pretending to be weak and that made all the other tributes leave her for last. Then she unleashed her full potential and violently killed all the remaining tributes.
Gale does not marry anyone in The Hunger Games. He and Katniss talk about running away together and starting a new life in the wilderness, but they never officially marry.
This interaction was so surprising to fans because it's not in the books at all. While, throughout the series, there's some chemistry between the two, nothing ever comes of the tension in Suzanne Collins' novels. Beyond the kiss, nothing happened between the two in the movies either.
On a mission to infiltrate President Snow's mansion, Finnick dies and leaves Annie a widow. Later, it's revealed that Annie is pregnant with their son.
Yes, Katniss did develop an addiction to the morphling, on account of constantly being sedated with it, however, I wouldn't say that she was an addict. An addict is someone who goes to a substance (or whatever their 'poison' may be) under their own mind.
Johanna Mason developed an addiction to morphling while hospitalized in District 13 for the torture she endured in the Capitol. When she was weaned off, she instead dipped into Katniss's supply.
Finnick rushes to resuscitate him as he knows he needs Peeta alive to keep Katniss going. Another clue that he is in on the rebel plan comes when Katniss is about to kill him with her arrow, and he tells her, "remember who the real enemy is," which is something Haymitch said to her before the games.
Peeta used the dyes to paint a picture of Rue after Katniss covered her with flowers when she died. He says he wants to hold them accountable for killing Rue, and Effie tells him that that kind of thinking is forbidden. Katniss then tells the team she hung a dummy of Seneca Crane.
(Katniss recognizes her because she was also in the forest outside District 12 when the girl was captured, and she feels guilty that she did nothing to help.) As punishment, the Capitol cut out the girl's tongue and then forced her into a life of servitude as an Avox.
Catching Fire's Mags Flanagan was District 4's female tribute in the 75th Quarter Quell, along with male tribute, Finnick Odair. At 80-years-old, she was the oldest tribute.
Johanna remains in the Capitol for quite a while, and she and Peeta are tortured for information concerning District 13 and the mockingjay rebellion. While in the Capitol, Johanna's entire head is shaved, making her bald.
Peeta later explained to Katniss that Johanna did this to get a reaction, since she and the other tributes obviously saw Katniss as being the most "pure" of the Victors.
