It is not only humans which are possessed, but also animals, trees and other objects. By doing this, the evil Jinn hope to make people worship others besides Allaah. The possession of idols is one way to do this.
Not so long ago the world-wide phenomenon of Hindu idols drinking milk, shocked the world. From Bombay to London, Delhi to California, countless idols were lapping up milk. Ganesh the elephant god, Hanuman the monkey god and even Shiva lingam, the male private organ(!), all seemed to guzzle down the milk as if there was no tomorrow!
Unfortunately people were taken in by this (including Muslims) and many flocked to feed (?) the Hindu gods. Anyone who knows about Jinn possession, will undoubtedly know that this is a classic attempt to make people commit shirk (associating partners with Allaah). And it worked, as many people started to worship these lifeless pieces of wood and marble. Anyone with half a brain would say to themselves, ‘why on earth does a god need to be fed?!! Surely if Ganesh, Hanuman or Shiva were divine then they wouldn’t need feeding?’ However, such common sense seemed to be lacking as the Jinns played havoc with these gullible people.
 Ganesh, the elephant headed deity, seemed to be the biggest drinker! In fact it didn’t just stop at milk. At the time of these occurrences, a woman in India decided to see if Ganesh would drink anything else – so she offered him whiskey!! And Lo and behold Ganesh drank the Whiskey!!! Suffice to say, the woman was kicked out of India.
Source : Invitation to Islam, Issue 4, January 1998