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human
[Men In Black] Did K recognize James as J when he recruited him ?

*Spoilers ahead for the ending of MIB 3.*

I just watched MIB 3 and I'm a bit confused by the way it ends. It suggests that in the first movie, K either recruited James because he recognized him as the son of the dead colonel to which he proposed a job at MIB or he recognized him as J, the agent who helped him through the whole Boris affair, and recruited him to complete the story.

The thing is, which one is it ? And if he did recognize him as J, why'd he try to retire at the end of the first movie when he knew that it would either change the events of the future and fuck things up or that he'd just be back a few years later ?

Also sorta half unrelated, but what the hell was he doing when Boris changed the events of the past ? Did he know it would happen ? He opened his armory and grabbed a gun for some reason when it happened. Why ?

Also, why the hell did J even remember his past years with K ? The hardware shop guy hints that we'd learn why later in the film, but we never do.
gpt
Firstly, we know that it is not a time-loop, as Boris went back and caused changes, namely K's death, and non-deployment of the Arcnet.

So there are 3 timelines we have to consider:  

1. Original time-line. No-one jumps back in time, K arrests Boris the Animal, after J's dad is killed by Boris. K goes on to keep tabs on James, until he realises that he would make brilliant MIB agent material. K, upon hearing Boris has escaped, believes Boris will attempt to kill him for vengeance. K is correct in this assumption, but is incorrect in guessing *when*. Boris jumps back, creating the second timeline:  

2. Boris wins timeline. Only Boris jumps back, K dies, J somehow still got recruited (O still knew J), and J jumps back. Bogladytes invade, Earth is lost.  

3. Final timeline. K knows about J, but is unaware that little James is J immediately after the battle at Cape Canaveral. However, due to James' dad's sacrifice, he decides to keep tabs on James as he's growing up, make sure he has a good life, etc. As he does this, he begins to notice that James is starting to look more and more like a certain time-travelling partner of his from the future. He recruits him, and we're back to a relatively stable time-line, so long as K remembers to tip.  

The differences between the first and third time-lines are there, but subtle, with K having a little more knowledge.  

Edit: Also, for why J remembered, little James was there, he possibly even saw K killed by Boris, so J was in the "eye of the storm" so to speak. Everything around him changed, but he was protected from the changes. MIB ended up getting real lucky with that. If James hadn't been there t that particular moment, bam, Earth gone.