The actress, who also starred opposite Robin Williams in Popeye, has friends and neighbours in Blano, Texas worried because she spends night after night patrolling her backyard, convinced her home is a portal for little green men.
One local tells the Globe, "Shelley is such a tragic soul. I feel terrible for her and wish someone could step in and do something. She desperately needs help."
Blano residents tell the tabloid that 60-year-old Duvall, who hasn't acted since 2002, flashes her car lights in a bid to communicate with extra-terrestrials and "wanders around town... looking dishevelled, strange and totally crazy."
Another local says, "She mutters to herself and talks about aliens living in her body."
And a local hardware supplier adds, "One time she came in and asked for dirt and boards to block up a hole in her backyard because, she said, 'That's a portal into another dimension. That's where the aliens are coming in.'"