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
You forget 90% of your dreams.
256
If you hold farts in during the day, they'll just come out when you sleep.
16
Lack of water is the #1 trigger of daytime fatigue.
148
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Sleeping on the job is acceptable in Japan. It is viewed as exhaustion from working hard. Some people fake it to look committed to their job.
57
The human brain is more active during sleep than during the day.
28