Staying up all night wondering if there really is a dog.
Sparkie.
A watch dog!
So time would fly.
So they won't run out of time
Man: The thief was spending less than my wife. Police: Then why are you reporting it now Man: I think now the thief's wife has started using it!
A phoney friend!
A cramberry.
To stay under cover.
Because he was alfredo the dark!
Answer(/s "Someone who lays awake all night wondering if there really is a dog")
A person who stays up all night wondering if there is a dog.