Easy Money
(1983)

The formerly shy, virginal Allison (Jennifer Jason Leigh) loosens up and learns to love sex even more than her husband Julio (Taylor Negron), who can't keep up with her insatiable desire!

Meanwhile, it turns out that Mrs. Monahan (Geraldine Fitzgerald) wasn't really dead. She faked her death to see if Monty Capuletti (Rodney Dangerfield) could be made to clean up his behavior. Since he seems to have changed his ways and embraced clean living, Mrs. Monahan brings Monty and his family to live in her mansion.

While living in the mansion, Monty acts like a completely changed man, and charms his mother-in-law. But he hasn't really changed at all- at the end of the movie, he sneaks out to join his buddies to drink, smoke, eat pizza, play cards, and mock his mother-in-law.

Thanks John L!