The Vipeholm Experiments involved giving retards excessive amounts of candy to see if they got cavities.
It was funded by the sugar industry so the results weren't published until years after the fact.
That one where they told kids to punch a clown punching bag. What was the point of that? Humans being naturally aggressive should have been obvious. Even the most peaceful person will want to punch a punching bag.
That time they made everyone stick a piece of paper on their face and inject untested experimental drugs into themselves or everybody would die. Pretty good prank.