I've seen it happen twice in my career. One of the times it was a huge success, the other was a disaster.
The first one was probably a success because there was just one developer before, so there wasn't really any culture and he quickly got absorbed in the group that joined the project.
The second case wasn't that successful and the group that joined refused to adjust to the existing culture when it came to processes and guidelines, and instead tried to run their own race because that worked at the previous place they came from. They were all fired after a couple of weeks
The first one was probably a success because there was just one developer before, so there wasn't really any culture and he quickly got absorbed in the group that joined the project.
The second case wasn't that successful and the group that joined refused to adjust to the existing culture when it came to processes and guidelines, and instead tried to run their own race because that worked at the previous place they came from. They were all fired after a couple of weeks