Elon Musk is being sued for $258bn (£209bn) over accusations he ran a pyramid scheme to promote a cryptocurrency called Dogecoin.
The digital asset was launched as a joke in 2013 and was designed to mock Bitcoin.
But the cryptocurrency - also known as DOGE - hit the headlines after surging dramatically last year.
In a little over four months, Dogecoin rallied from $0.004 to $0.73 - a gain of more than 18,000%.
Musk regularly tweeted about DOGE during this period, and on the day the coin began to fall, he described it as a "hustle" on the US comedy show Saturday Night Live.
A complaint filed in a New York court adds: "Musk used his pedestal as the world's richest man to operate and manipulate the Dogecoin pyramid scheme for profit, exposure and amusement."
The plaintiff wants to represent those who have lost money through Dogecoin since 2019.
