Same thing different name to me. Ken (an echo) is more unique than Dr. Mario (a clone) was in Melee. There isn’t really much consistency with what qualifies as what. Then we have Alph, the Koopalings, and Hero as alts and it’s all kind of a mess. I just group them all together as characters that are strongly based on the foundation of another existing character, whatever their label.
I actually find it pretty clear.
- If there is a difference in height or weight, it can't be an Echo nor an alt: it's a clone.
- If there is at least one small change in animation, like in the taunts, it can't be an alt: it's an Echo.
According to this, Ken is not an exception. He could be a clone, but he doesn't have to. Same could be said for Lucina and Chrom.
Dr Mario cannot be an Echo since he weights more than Mario.
Pichu cannot be an Echo because he is smaller an lighter.
Alph and the Koopalings are not Echoes because all their animations are the same as their model's.
I have a small doubt for Dark Samus, but I think she weights exactly the same as Samus, doesn't she?
Also I don't know about the Heroes.