Your friends should have been here by now, shouldn't they?  
Shouldn't your friends already be here?
It's good that your friends are already here.
I like the idea of making dresses for children or even writing children's books.
The plane is crashing.
TWO PEOPLE PLAYING ON A RUG.
Three people eating lunch at an outdoor picnic table.
More than one person is making some music here.
The dog is carring a purse