Interface of a class that extends MovieClip

I am instancing an interface IJohn of a class John that extends MovieClip: I am receiving the errors that tells me that “addEventListener” is an unknown method, obviously.
How can I fix this without putting all EventDispatcher methods in IJohn and John?

Plus, if I try to addChild the interface instance it tells me I am trying to use a IJohn as a DisplayObject, as the interface does not know that it is implementing a MovieClip.
So, how can I use the MovieClip properties through an Interface instance?

Thanks