Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
15
Lack of water is the #1 trigger of daytime fatigue.
148
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
The higher someone’s I.Q. the more likely they are to be sleep deprived.
29
If you hold farts in during the day, they'll just come out when you sleep.
16
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23