E.g. using it as a song title, using these names in my own games, as a bussiness name P.S.: I’m asking about just the names not other characteristics of a fictional universe.
E.g. using it as a song title, using these names in my own games, as a bussiness name P.S.: I’m asking about just the names not other characteristics of a fictional universe.
Song title, probably not. Names covered by a trademark or existing copyright or with an obvious connection to existing IP, probably yes. Especially if you’re making money with it or doing something that can be construed as competition with the trademark or copyright holder. The specifics will depend on the details but its usually not a good idea, or if you do it then be prepared to cease and desist because you will likely get a letter in the mail telling you you’re getting sued if you don’t. If its obvious parody or satire that changes things a bit, or adds further complications and a potential defense you can use if sued.
Probably the most famous example is Barbie Girl. The musical group Aqua created the song and was sued by Mattel. The toy company won the rights of the song because it was specifically using their product IP. They referenced specific features of the toy line, including the names of Barbie and Ken. Mattel was able to demonstrate that the song harmed their IP. That was the key feature IIRC. In the end, I think that it was ruled that the song was clearly a parody. So any harm that was caused, people would not assume was connected with the real-world toy.