I believe there is a bug in your object model for handling super. I have tested it and it does indeed work incorrectly (although not in the way I expected it to work incorrectly). Basically, your super calls only work if your class tree is 1 level deep. As soon as you have something like Animal -> Horse -> BigHorse, then it breaks down. This is because super() gets translated to:

this.constructor.prototype.NAME.call(this, args)

So, if we had move on BigHorse, Horse, and Animal, BigHorse would call super (resulting in Horse's implementation being called), but then Horse calls super which again calls Horse's implementation, since this.constructor.prototype still points to Horse.prototype. Thus, you can't continue climbing up the chain. When I tried it though, it seemed to just skip the intermediate classes and go down to the base class, which is of course equally broken. We used to have the same problem a long time ago in Objective-J. The fix is pretty simple, you should just inline the actual class name when dealing with supers:

Horse.prototype.NAME.call(this, args), which then calls: Animal.prototype.NAME.call(this, args)

Hope I avoided you some pain with that one. I remember 3 years ago not understanding why on earth my code was broken and thinking it was algorithmic for the longest time until I realized the entire underlying parts were broken.