Right then. Let's jump straight in with two extremely popular theories.

First one: How Scar became Scar

Ok then, so theory one is the one that uncountable fans use. Scar used to be named Taka, he was overshadowed by his brother, Ahadi either hated him and mistreated him or just lost his temper with him once and slashed him across the face.

There. Well, suddenly, everyone's like; "I feel so sorry for Scar, because he was abused by his father!!"

Untrue, dear fans, very untrue (If that's a word) These things need to be researched first before you go backing up villains here (NOT that Scar isn't cool!) Anyway...

The theory where Ahadi slashes Taka across the eye is FAN. MADE. For a start, only things in the movie itself should be considered complete and utter canon in my opinion. The name Ahadi came from the now well-known book-series, THE LION KING SIX NEW ADVENTURES, just like the name Taka, which was never mentioned in the film anyway. The thing is, this same book series seems to encourage the idea that Scar/Take was just very jealous and got the scar on his eye from a waterbuffalo when his plan to get Mufasa in trouble failed.

This, as far as I know, is the only theory to Scar's scar in books/ comics. But then again, Disney never actually agreed with these books, so in some ways, you could even say the books were fan-made, just published. You can use whatever name you want for Scar or his father, but there are NO official theories to his scar, as Disney probably never thought about it officially anyway. They never said in the film about Scar being Taka and becoming Scar just because he was abused, and it's not much of a story that Disney would put in children's films; Disney films are usually quite simple, and having the idea that there's a lot more to Scar would just confuse young children and drive them away from the point of the film.

Whatever you say,  the theory that Scar got his scar from his own father is pure fan theory. I don't see it in the movie or in any books published by Disney, so this theory is, and will remain, FAN. THEORY.

I don't mind the theory much, but please remember: There is no solid theory to Scar. We're all just making up "What if's"

Second: Kopa

Right then, first of all, Disney was never going to use Kopa in the second film. Kopa is a character from a book series that Disney never even stated that they supported it and was released before the 2nd film. Disney might not have even known about it then, anyway!

Apparently, Disney was going to use a lion called Tanabi for Simba's son, then changed it to Chaka while they gave him a sister-Shani-then decided to ditch the son and focus on the girl, giving Shani the name Aisha, but when they realised that Aisha was the name of the yellow power ranger (I think? Yellow, was it?) they changed it to Kiara and VOALA! BUT. but this may not be entirely true, due to internet not being very trustworthy these days xD So don't think that this is complete and utter fact!!

Kopa was just the author's interpretation of Simba and Nala's son, and like the rest of the TLK6NA books, hasn't been proven true by Disney. You may say that the two lion cubs at the end of TLK and beginning of SP look totally different, and I agree with you, but the explanaiton is that Disney might not have really thought that much about the 2nd lion king film at the time, and just put a cub in there without much thought to it's design to complete the film nicely, so sort of made it look like Simba because they never thought about more specific designs. Someone named it "fluffy" as a joke, but when SP was made, it was made by different people, which might explain the differences,

Have as many fan theories of Kopa if you want, I do as well, but please don't go on about how Kopa is official and should have been used instead of Kiara and how he is the true king....

because he's not even official to the movies.

That'll be all *Takes bow*