Tesla CEO Elon Musk says he brought a feature back to the company's top-of-the-line sedan only after the change received negative feedback from his offspring. Speaking to attendees of the Automotive News World Congress today in Detroit, Musk said that one of his kids called the Model S "the stupidest car in the world," because it didn't have reading lights in the back. The feature had originally been removed because Musk and others believed people would use backlit devices. One of his five kids thought (and said) differently, and the lights were brought back.

Tesla originally said the removal of the lights was to increase the headroom in the backseat area, something it was able to accomplish while keeping the lights, but the company managed to ship out some cars to customers that did not have them. Tesla ultimately offered to install the lights to those customers at no cost.

Musk also hopes Tesla will be profitable by 2020

Along with lightbulbs, Musk discussed a number of rather serious issues facing Tesla, including the possibility of the company becoming profitable by 2020. Musk skirted questions surrounding just how many cars Tesla was selling, saying the company's target for last year was to sell 33,000 vehicles. "We sold, in terms of cars, far more than that," he added.

Following the interview, Musk fielded questions from a pack of reporters, saying that the company's forthcoming Model 3 will cost around $35,000 without any tax credits when it's released in 2017. Musk also discussed various energy sources, including hydrogen and the status of the company's Gigafactory project. Musk again called hydrogen fuel cells "extremely silly," and outright dangerous. "It has extremely low density, it's invisible, you can't even tell if it's leaking, it's extremely flammable. Hydrogen is an extremely dumb [energy source] to pick," he mused. "You might as well pick methane." As for the Gigafactory project, which will mass-produce batteries when it opens in 2020, Musk said it will take years before it's capable of producing enough low-cost cells to sell to other automakers.

Musk's appearance came alongside the North American International Auto Show, which is taking place in Detroit during most of this month. Other speakers at the Automotive News World Congress include General Motors CEO Mary Barra, Jaguar president and CEO Joe Eberhardt, and Chris Urmson, the director of Google's self-driving cars project.

Chris Ziegler contributed to this report.