He has thought us many things - just one look at his quotes list shows us that. But one thing English language learners can learn and use from the late Robin Williams is not to rely on scripted answers. He was known for coming up with many his best known lines on the spot, as I am sure many actors do, but Robin Williams had a special talent for this.
What I am getting to here is do not just rely on scripted conversation answers in grammar or exercise books to improve your English. Because simply they won't. And you will sound very dated.
This applies to all areas of English. If you can use your skills to construct an intelligent and rememberable answer, it will be infinitely better than just repeating a phrase or a sentence you read in an exercise book. For example, in a job interview or in an exam.
Another problem is that most everyday conversations that happen in English are not like anything that you see in grammar and exercise books. And neither are the questions or answers.
Also by challenging yourself to think like this and increase your English level will be much more beneficial for you than simply repeating something you saw.
To finish this post, try to challenge yourself to think independently in English- of course it is going to be difficult but you will improve a lot quicker.