Really interesting talk about Object-Oriented Programming in a time when I wasn't even born! It´s really amazing how the tools that I use every day were created so many years ago. It's a good talk to understand the philosophy behind OOP and specially Smalltalk and Objective-C.
The most curious thing for me is see how types systems were not really important because of message sending. Everything are objects and the only thing that you know is that they understand a protocol.
Another interesting thing that is mentioned at the end is blocks. A really cool feature that allow you to deifne your own code semantics as we see in Swift with clousures.