When people up north say something like, "Well now, that opens up a whole new can of worms" it means that until you told the whole story, they didn't get their thought complete.
But if you visit us here in the South and somebody says something like, "I'm just about ready to open up a big can of whupass on you, Mister", you won't have time to do any thinking about it. You just leave, fast.
-I.M. Moleturd