I've always been a fan of Vitani/Kopa. They just make sense :3
I love Vitani's design. She's like...a sort of 'ugly pretty'. She looks very unique and she could be considered ugly by those who want the same looking lioness over and over to be considered pretty. She's got a big snout, freckles, fringe, a rough voice, and dark rims around her eyes, and yet, the blue eyes, coloring, and slim build help to make her beautiful. I like her sort of attitude. She doesn't take crap from anyone (except maybe her mother, which, even then, she stands up to Zira in the end), she treats Kovu fairly well, she knocks some sense into Nuka, and apparently has a sense of responsibility ("Nuka! Where's Kovu?"). She's a good fighter, as well. What isn't there to like about her?
