[quote="greyspot":lbjysplq]It works, and this is somewhat unrelated, but if you change the target from the overlap from the green family to GreenSprite, the game crashes. Why is this? Families work here, but I don't know why they do.[/quote:lbjysplq]
Families are a way to group objects together. When you do that, you can test conditions and perform actions on the group. The group is treated as a separate entity where picking is concerned.
In this case, the family is a group of one. The sprite is the only object in there. But this means that we can now refer to the object in two different ways... by it's object-self, and by the group-self. So... now you can check if Sprite is overlapping Family without any conflict. It's just a trick to make instances of the same object interact, it's not really what Families were designed for.
For more info on picking, and the Selected Object List, check out the wiki:
http://sourceforge.net/apps/mediawiki/c ... ct_picking