A few moments after Billie throws the knife and it sticks in the wall, it moves from side to side a bit, as though a string were attached to it and pulling on it.
Piper claims that she was single seven years ago, right before the charmed ones gained their powers, but she was engaged to Jeremy (a warlock).
When Paige says, "This is real. Deadly real," Billie sneers and says that you "can't use an adverb with a noun." "Real" is not a noun, it is an adjective.