Well, Selphie and Vanille are both the 'happy and cheery' type.

And coincidentally, they both have a killer ability. Selphie`s The End can 1 HIT KO a thing and Vanille`s Death can also 1 HIT KO a thing.

What does this mean? Could it mean that these 'happy', 'cheery', etc emotions have a strong emphasis that they are very powerful?

This also made me wonder about the Rinoa=Selphie theory. If the above is true, could it mean that Rinoa`s was originally the 'happy and cheery' type? Let`s imagine... a Happy Selphie with Squall, her cheering him up, loving him, etc. Hmm, yeah. I see why Square changed thier mind. Changed Rinoa`s personality and gave her ability to Selphie`s instead.