Prompt: Who are they?

They say life is short
They say you can't avoid death or taxes
They say you can't take it with you
They say diamonds are a girl's best friend
They say dog is man's best friend
They say it's a dog's life
They say it's raining cats and dogs
They say black cats are bad luck
They say walk between the raindrops
They say don't walk under a ladder
They say beauty is in the eyes of the beholden
They say "'scuse me while I kiss this guy"
They say "wrapped up like a 'douche' you know the rumor in the night"
They say the night is young
They say the young and the restless
They say your mouth will be washed out with soap if you say that again
They say cleanliness is next to godliness
They say at most there is one god
They say let go and let god
They say go with the flow
They say take me to the river
They say you can never step into the same river twice
They say once bitten twice shy
They say once upon a time
They say and they lived happily ever after
They say the end