The crowd at darts matches can often be a little bit boisterous, but we've never seen anything like this.
A match between Simon Whitlock and Michael van Gerwen in Melbourne, Australia, had to be halted as fans in fancy dress ran riot.
Fans dressed up as Batman, Robin, English knights, Fred Flintstone, Oompa Loompas and others all got involved in the madness.
Police finally arrived to calm the situation, but not before the plastic chairs being used in the main part of the arena were thrown everywhere.
We can't confirm it, but we suspect drinking might have been involved.