I've known a few people who gave TED talks. They REQUIRE you to rehearse and memorize every single action and word of the talk. It often looks natural, but it's been done a hundred times before. You're not allowed to use note cards or teleprompters, etc. and you have a clock with a giant timer counting down in front of you. If you don't prove to them you know the speech well enough they won't let you do it.