GremlinsGremlins

A father gives his son a strange pet called a mogwai, along with three rules that must be followed.

Inventor Rand Peltzer (Hoyt Axton) is looking in Chinatown for a Christmas present for his son Billy (Zach Galligan). In an antique shop he finds a small furry creature called a mogwai. The shop's owner refuses to sell it, but his grandson secretly does, with three warnings: the mogwai must stay out of bright light, must not get wet, and must never eat after midnight. Rand names the creature Gizmo and gives it to Billy in Kingston Falls, where Billy works at the local bank and worries that his dog Barney will be put down by the widowed Ruby Deagle.

Story written by Evenitto from TMDB and Wikipedia