In doing geneological research, I found a patent in my mother's name for a pack of cigarettes with attached matches from 1941; at 98, she had no recollection of it at all. I always surmised one of her uncles, who had had failed businesses, came up with it and put her name on the patent in case it made any money.
As nelkins said, this can get you in trouble. Inventorship is a legal determination and inventors are limited to those who have made a material contribution to the conception of the invention - see http://goo.gl/w0KAt. This often has the effect of keeping lab techs (who do the majority of the grunt work generating experimental data to support the patent claims) off patents. Knowingly adding the name of someone who did not contribute to the conception of the invention can result in the patent being cancelled because of inequitable conduct.