From WENN.com

The actors, along with Betty White, Carrie Fisher, Leonard Nimoy and Patrick Stewart, agreed to tape a limited number of custom-made messages after veteran entertainer Ed Asner came up with the idea to raise funds for advocacy group Autism Speaks.

The personalised messages won't come cheap - they are priced at $299 (£187) each and are only available for one week from 3 December (12).