On closer inspection I saw that each of the sports was being related to Newton's Laws. As I read the posters it was clear students had simply found the law(s) on Wikipedia or some other site and then did their best to apply them. Sometimes the results were the "t-shirt versions" of the laws, i.e. short, simple and catchy, but incomplete. Such as:
But, mostly it was the application of the law that was wrong - no surprise there.
Lets hit misconceptions head-on. Not in the contrived language from a teacher, but in the language of peers (albeit younger peers). I would love to have a collection of student quotes on a full range of physics topics... I can see these as material for test questions, homework, or class discussions.
As a side note the quality of student work that is posted in public spaces is a big topic of discussion at our school.