There are three simple rules for owning a Mogwai, as explained by Mr. Wing to William Peltzer Sr. in Gremlins (1984) and reiterated by William Peltzer Jr. in Gremlins 2: The New Batch (1990).

The RulesEdit


A Mogwai


Gremlins. The result of not obeying Rule 3.

1. Do not let it get wet
Contact with water causes a unique chemical reaction in the Mogwai (and in its Gremlin form), instigating instantaneous parthenogenesis. If subjected to prolonged contact with water the creature will multiply almost exponentially. Production of offspring occurs differently depending on if creature is at Mogwai or Gremlin stage.
Mogwai offspring are produced as furry, fluffy balls emitted at high-velocity from the creature's upper back. In Gremlin form however, the offspring are instead grown rapidly in transparents sacs, also on the creature's upper back.

2. Do not expose it to direct sunlight.

Contact with sunlight causes intense physical pain for the Mogwai species. If exposed to 'bright lights' they will immediately seek shelter in the shadows. 
The Gremlin sub-species is highly allergic to sunlight exposure. Brief contact will cause severe burns and prolonged contact will kill them. This has been proven as the one truly effective way to stop a Gremlin outbreak. 

3. Do not feed it after midnight.

If a Mogwai eats after midnight it goes into a pupal stage, ultimately emerging as a member of the malevolent Gremlin sub-species.  If present in sufficient numbers (usually due to the contravention of Rule 1), Gremlins can cause significant risk to public wellbeing.