`@popovers` as a field on the class is a class variable (if you look at the JavaScript, it is on the actual Popover object, not the prototype).  In order to reference it from an instantiated object, you have to refer to the actual class, since it's not part of the `prototype` chain.  Coffeescript compiles the code in a way that makes `@constructor` a reference to the parent object.  There is no `popovers` on the instantiated objects.