We have got a friend in London, perhaps you know his name, George Harrison. His house is a palatial building — he is a very rich man — but the former owner of the house is living there as ghost. This is practical. He was very rich man, the owner of the house, former owner of the house, and he invented so many things, so he got enough money and he was too much attached to the palace. The whole money he acquired, he constructed that house. Now after death, due to his too much attachment to that house, he is living there as a ghost. This is possible. Not only as ghost, but sometimes as rat, as cat, as a snake — this is the law of nature.

If you have got too much attachment for this material world, then you will have to come back again, and according to your karma you have to accept a body.

From Srila Prabhupada’s lecture on Srimad-Bhagavatam 1.2.6 – September 17, 1971, Mombasa