A group of Pokémon Go fans are threatening to take the makers of the game to court after attending a festival for the game where lots of things went wrong.
They want the company to pay them back for the cost of travelling to the festival.
Niantic, who make the game with Nintendo, put on Pokémon Go Fest in Chicago, in the USA, last weekend. Unfortunately for the almost 20,000 people who attended, there were lots of problems.
So many people were in a small area trying to play the game that mobile phone networks couldn't connect people and Niantic also discovered there were a number of bugs in the game that affected people trying to play the game at the festival.
Things got so bad that at one point people were chanting "fix our game!"
One boss from Niantic apologised to fans, saying "We know that this is not the day that we had all envisioned."
Now some of the people have started the legal process to get the company to give them back the money they spent getting to Chicago to attend the festival. A lawyer called Thomas Zimmerman told Polygon that "people came from out of state, many people from other countries." He even said: "I talked to someone who flew in from Japan."
Zimmerman says Niantic should repay those fans, because, "would they have done that had they known that … they weren't going to get the experience that was represented?"