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... Employees stationed elsewhere oversaw many of the interactions between the humanoid machines and attendees of last week's "We, Robot" showcase near Los Angeles, said the people, who asked not to be identified discussing company operations. The Optimus prototypes were able to walk without external control using artificial intelligence, the people said.

Tesla representatives didn't immediately respond to requests for comment.

Some attendees said on social media afterward that the robots had help and at least one video posted online purportedly from the Oct. 10 Cybercab event shows an Optimus bartender acknowledging that it was being "assisted by a human."

That wasn't stated by Chief Executive Officer Elon Musk during his remarks on a webcast.

The use of human input raises questions over the capabilities and market readiness of the bot, which Musk said last week he expects to be "the biggest product ever of any kind." The CEO told the crowd it will handle many household tasks and could eventually be available to consumers for $20,000 to $30,000 each.

"What can it do?" Musk said. "It can be a teacher, babysit your kids, it can walk your dog, mow your lawn, get the groceries, just be your friend, serve drinks. Whatever you can think of, it will do." ...