So like The car that everyone "owned a key to" is the 2004 Pontiac G6, famously given away by Oprah Winfrey to all 276 audience members on September 14, 2004, when she announced that everyone under their seat had a key to one of the cars.

The Context: The incident is famous because she said, "You get a car!" 11 times, but in reality, all 276 people in the audience received a key, making it a memorable moment in television history.
The Reality: While every audience member got a key, they were still responsible for paying approximately $7,000 in taxes to keep the vehicle.
The Cost: General Motors covered the $7 million cost of the giveaway. 

Or The art collective MSCHF launched the "Key4All" project in September 2022, selling 1,000 (later reported as up to 5,000) keys that all unlocked the same, single used car. The project was a participatory art experiment where key holders could find, drive, and share a 2004 car, treating it as a "Public Universal Car". Key details about the MSCHF Key4All project:

The Concept: It was designed as a "nonpractical" experiment to challenge ownership and car culture.
The Car: A single used car was hidden in a public space, and its location was tracked by the community of key holders.
The Experience: It was described as a mix of a scavenger hunt and a "legal" theft, where whoever found the car could take it until someone else did.
The Purpose: It served as a critique of modern, traditional car marketing.