A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Bats sleep 18-20 hours per day.
5
If you hold farts in during the day, they'll just come out when you sleep.
16
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
Lack of water is the #1 trigger of daytime fatigue.
148