The exclamation mark means they need to do something.
You could also mistake it for a tooth or a skull, which means it is sick. I've heard of it, but I don't think you would though..
(Woah, right when I was typing that, I got a knock on my tama door.. It was poo in an envelope!)
Edit:
You speak japanese!
Konnichiwa!
Genki des ka?