Luigi deserves his own animated series. He’s a far more interesting and developed character than his brother Mario, the Nintendo equivalent of Mickey Mouse whose character is so protected he’s not allowed to have faults. Luigi is at heart, kind of a coward, but he still does heroic things, which makes him an excellent subject for a show.
A show based on the Luigi’s Mansion series likely wouldn’t take place in just one mansion but have Luigi chasing ghosts with his trusty Poltergust ghost-sucking vacuum-like device and uncovering mysteries that could take place over one episode or several.
I picture it like The Thirteen Ghosts of Scooby Doo, where the ghosts were finally real. What made Scooby Doo and Shaggy interesting characters that stood out among the group is that there were unabashedly absolutely cowardly. They did not go seeking danger, they didn’t like it, and they wanted to get as far away as possible, And it’s not that they still couldn’t be heroic, it just was not their first instinct by a long shot.
Luigi would have a similar arc, maybe every episode (or at the start of every story arc if it’s over several episodes) he’s not looking for ghosts, but he keeps running into haunted places no matter where he goes. Take the fun and playful nature of the Luigi’s Mansion series ad you have a great concept for an animated show.