Cool. Every time you click on an object if you told the previous object you clicked on to do something, that object also does it though. There needs to be a deselection? And what's causing the lag?

getX() i believe is only a method for an actor and what you have are objects. ..and i think you should post things in the greenfoot discuss for help on things

your list is called NGoo set Goo to NGoo.get(someIndex) then do NGoo.remove(someIndex)