I've been wanting to write on this subject for a while, I finally have some time off work, so warning it's going to be a bit of a long post.

Kopa is one of my favorite characters, but when it comes to cannon vs. non-cannon the only place that Kopa officially exists is in TLKSNA. When I was a child I thought the cub at the end of TLK was a male, because I figured Simba would have a son to continue on his line. Kopa is one of those topics that's very interesting because I do not think Disney was really thinking clearly. The MIGHT have assumed the cub was a male before making SP because they did not plan on making another movie. It was just to show Simba and Nala had balanced out the circle of life. However, Disney, in my opinion made a big error in trying to say the cub at the end of the first film was Kiara. The ceremonies are far too different, and even I would not buy that they're the same cub. Part of the problem is that different animators worked on SP and I think they were in a rush to create a sequel to one of their most popular and successful films. Disney decided to fudge and change things because they wanted to have a female lead, a princess rather than a prince and because Romeo and Juliet was what SP was based around. So, officially by the Disney company, Simba's only cub is Kiara.
Now onto Kopa: Even though to Disney he is not official or does not exist, I still think Disney could acknowledge that lions generally have more than one cub. Scar and Mufasa were brothers. I do believe they do one cub for convience. However, I think Disney needs to think of more than just the bottom line. My theory (now it's my theory, not officially) is that Kopa was killed by Zira so that Simba would be deprived of an heir. I think this was part of the reason that the outlanders were banished from the pridelands. I like the pound of flesh line by Zira, it points to her doing something a bit more sinister. I believe Kopa would have been a facinating character, perhaps Kopa somehow struggling with the idea of taking the throne. I love Kopa because he has a lot of cub Simba and Nala in him. I like Kiara, but I think Disney made her too much of a damsel in distress. I am also partial to the idea that Kopa was able to escape, even though he was near death. I like to think he would join a rogue pride and someday come back to claim his place at the throne, confronting his father. I also like the idea of him with Vitani.
Dog Mom to Misty, Sango, Tami, Abby, and Kawaii.
Three Angel Babies at the Rainbow Bridge: Mija, London, and Olga
