Simone Lenoir

Simone Lenoir is the hidden main antagonist of Scooby-Doo on Zombie Island. (Even though she wasn't revealed to be evil until the climax). She, like Lena Dupree and Jacques, is a werecat living on Moonscar Island, who must drain the life force of victims lured to the island every harvest moon to preserve her immortality.

Past
The human Simone Lenoir lived in the 18th century, and was one of a group of peaceful settlers who lived on Moonscar Island and worshipped a cat god. One night while the settlers were celebrating a bountiful harvest, the island was raided and pillaged by Morgan Moonscar and his pirates; the pirates drove all the settlers except Simone and Lena Dupree into the bayou, where they were devoured by alligators. Devastated and vengeful for what Moonscar's pirates had done to their friends and their home, Simone and Lena invoked the cat god to curse the island and give them revenge upon the pirates. The cat god granted their wish by transforming Lena and Simone into werecats, who subsequently killed Moonscar and his pirates.

However, this was not the end of it for Lena and Simone, as they afterwards found that the cat god's curse had turned them into werecats permanently, cursed to live forever through draining mortal victims' life energy every harvest moon. So for the next two centuries, Simone and Lena would, every harvest moon, drain the life energy of Moonscar Island's human inhabitants; if there were no others on the island at the time of the annual harvest moon, Simone would have Lena find and lure tourists and visitors to the island to drain. A side-effect of the werecats draining their victims' life energy was that it would curse the victims' souls so they would rise as zombies every harvest moon and unsuccessfully try to warn the annual victims off from suffering their fate. Lena and Simone also at some point recruited Jacques as their ferry driver for bringing lured victims to the island, and granted his wish for immortality by passing the werecat curse onto him.

Scooby-Doo on Zombie Island
The werecats' latest to-be victims in the present were Mystery, Inc. when the gang were lured to Moonscar Island by Lena in Daphne's search for a real haunting for her TV show. As the gang settled in, Scooby's antics and his destructive pursuit of Simone's cats all over her property was a running irritation for her.

On the night of the harvest moon, when the zombies of the werecats' previous victims rose and went after the gang to try and warn them, Lena lured Fred, Velma, Daphne and the human gardener Beau to her and Simone's underground voodoo dungeon, where the two werecats captured and bound them using voodoo dolls to be drained. The gang managed to slip free before Simone and Lena could drain them, in the commotion when Shaggy and Scooby, followed by Jacques and the zombies, fled into the dungeon. Lena and Simone almost succeeded in draining Shaggy and Scooby, but were stopped when Velma and Daphne reconfigured the voodoo dolls and used them against the werecats. Jacques, Simone and Lena eventually overcame the zombies' efforts to stop them and cornered the gang to drain them, but just then, the midnight phase of the harvest moon ended. With the harvest moon's midnight phase having ended before the werecats could drain their victims, Simone, Lena and Jacques' immortal lives were taken away and they decayed away and perished; ending the cat god's 200-year-old curse, and freeing the souls of the werecats' zombified past victims to rest in peace.

Trivia

 * Simone and the other werecats are the first Scooby-Doo villains to die, followed by Ben Ravencroft and Phantom Virus.