Something the internet is awash with is fan art - drawings or stories or songs written about another property that particularly resonated with the artist. It’s a sort of tribute to the original work.
Fangames are another category of fan art. Generally, these are small projects and only available on PC. However, because the scale of these kinds of projects can be much larger than just a painting or a song, the original creators sometimes shut them down with a Cease and Desist order, preventing the projects from ever being finished. One of the first fan games to get shut down like this was a complete conversion of the PC game Quake to be a sequel to the movie Aliens, released in 1997.
A more recent example is a fighting game that was originally based on the kids’ show “My Little Pony.” It had all the main characters from the show, and was shaping up to actually be a really competent fighting game. However, shortly before release, Hasbro sent the developers a Cease and Desist. Instead of abandoning the project altogether, they continued with new, original characters, designed by the same person that created the TV show, and voiced by some of the same actors. The game, “Them’s Fighting Herds,” is now available on PC.
Other times, fangame work gets more positive attention. Fans of the Sonic the Hedgehog series have been creating fangames for 20 years, many of which were better than the originals. Sega eventually took notice, and hired several creators of these fanworks to create Sonic Mania, which ended up being a standout hit. The game was developed by someone who learned how to program partially by making his own Sonic game engine, the levels were designed by people who had designed levels in several Sonic fan games, and the soundtrack was written by a man with a YouTube channel full of covers of Sonic music going back almost 10 years.
I guess, sometimes, fans just know what their fellow fans want more than the original creators themselves.