Every time you want to make a table listener, the table has to have a method with the same name as the event. In this case you would have to call it function Character:collision(event). Then it will work with the addEventListener line you have now.
Every time you want to make a table listener, the table has to have a method with the same name as the event. In this case you would have to call it function Character:collision(event). Then it will work with the addEventListener line you have now.