Don't forget this question is still on the go:
John dropped in to visit his friend Frank, and found him snoozing on the couch. There was fresh blood on the ceiling above his head, but nowhere else in the room. John anxiously woke him to check his condition only to find that everything was fine. How could Frank's blood be on the ceiling but nowhere else?
I´ll take another try on this one...
The fresh blood comes from a smashed mosquito that drenched it´s thirst at Franks blood. Then he smashed it and not disturbed by the noise anymore he fell asleep...