Fear Doesn't Ride a Donkey(1973)

Original title: El miedo no anda en burro

This funny Mexican film tell the tale of a family who will do anything to get rid of the rich old lady who sits at the head of the clan. All the hilarious members want a piece of the very lucrative inheritance money. What they don't know, however, is that grandma has left all of the money to her trusty dog.