Please, I can't understand this block of code

Is there any reason why he would do this?

the puppeteer class is not a parent class of the dog, alien or human class. So, how on earth is he able to say "puppeteer.dog" etc. And what is the use?

It is from a youtube video, explaining the saying "program to an interface, not an implementation".

Cheers!

Please look at the code within the oval