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
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Cows can sleep standing up, but they can only dream lying down.
745
You forget 90% of your dreams.
256
There's a love mattress that is specifically designed for couples who sleep on each other's arms.
12
Quick naps not only improve your alertness, but they also help in decision making, creativity and sensory perception.
149
If you hold farts in during the day, they'll just come out when you sleep.
16
Termites work 24 hours per day and they do not sleep.
57