Also taking part in the effort -- for which celebrities record custom messages for a donation of $299 to the non-profit organization Autism Speaks -- are Jack Black, Michael Dorn, Peter Dinklage, Vin Scully and Zachary Quinto.
Celebrity messages may be bought at http://shop.autismspeaks.org/soundoffforautismspeaks through Sunday.
Fans can specify what they want their chosen celebrity to say in the message and Autism Speaks will send them a digital file once it has been recorded.
Last year's "Sound Off for Autism Speaks" campaign raised more than $100,000.
It was spearheaded by Ed Asner, whose son Matt serves as executive director of Southern California for Autism Speaks. In addition to Ed Asner, participating celebrities in the 2012 campaign included Will Ferrell, Morgan Freeman, Carrie Fisher, Tom Hanks, Derek Jeter, Leonard Nimoy, William Shatner, Patrick Stewart and Betty White.
"Last year, I got together with Matt and we discussed what my friends and I could do to support the important work of Autism Speaks," Ed Asner said in a statement Friday. "We decided that bringing together a group of celebrities with great voices to do a kind of 'voiceathon' would be a fun way to raise awareness and funds for the autism community. The campaign was such an overwhelming success and received so much positive feedback we had to do it again."
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