I forgot that the IX timeline mentioned Kuja's age, and I guess the Compilation has finally given a narrow enough timeline to confirm Sephy's actual age. Never heard that Ex-Death was 300 years old though, but I guess we might be talking about the tree itself. As for Kefka...

Which Ultimania? I have the original character guides for VI and they give no inclusion of his age, hell, the VI timeline conflicts with another guide given on Gestahl's age, so I wouldn't be surprised if a few things got retcon out over the years.. I've also heard that the Thamasa orphanage thing is unreliable cause the source is from a fan-fiction site. So if you can give a source I would be appreciative as it would help in another thread I'm working on.

Also, I've already mentioned the non-humanoid characters bit. As for Kefka's laugh in VII and CT. It is the same as his laugh but in both cases, the laugh has been altered by either slowing it down or raising the pitch. Yet you can distinctly tell its the laugh. For those wondering, Sephiroth already mentioned that the laugh in VII comes from the Ghost Hotel in the Gold Saucer, in CT, it's from both Norstein Beckler's Tent of Wonders at the Millennial Fair and Ozzie uses a variation of it as well.