River Styxx makes her debut in the animated series in the TV special Haunted. Her English voice actor is Ashley Peterson.
River is the first to meet Draculaura and the other non-ghost, or "solid," students of Monster High as they attempt to follow Spectra Vondergeist back to the Ghost World to see why she was so nervous about when Draculaura mentioned she was being haunted. When Spectra explains the reason to River, River remembers the story of the Red Lady of ghost legend, and tells the tale to the other ghouls. Soon after, River's skiff is attacked by Vandala Doubloons and her skeletal pirates as part of a class project that Vandala has River sign the form of to ensure Vandala gets credit for the attack. Soon after, they arrive at Haunted High, and River helps show off the Detention Chains that many students are now wearing that prevents them from leaving Haunted High until they work the chains off with extra homework of chores. Traveling to the Creepataria, they meet up with Kiyomi Haunterly, and bear witness to being introduced to Principal Revenant and her Hall Moanitors. When Draculaura and the other non-ghost ghouls cover is blown, River assists with getting them back to Monster High on her skiff. Later, after she brings them back following them becoming ghosts themselves, sans Sirena, they regroup with Vandala and Kiyomi, and then find shelter in Porter's secret room. Their reprieve is short-lived before they are found by Revenant after Porter seems to sell them out, and when Revenant assigns her Hall Moanitors to go to Twyla's house to retrieve her father's Boogey Sand, River makes the mistake of bringing up how they are going to get there since she is not going to take them in her skiff, especially now that she's in Detention Chains and unable to leave the school, forcing the Hall Moanitors to commandeer it instead. River goes to confront Porter with the others, only to forgive him when he reveals he swiped Revenant's key to the Detention Chains and transfers all of their chains to himself as punishment for his betrayal. River helps the others in freeing the Monster High students wrongly incarcerated in Haunted High by Revenant, and joins them in trying to get back to Monster High on Vandala's ship before the Hall Moanitors do on her skiff. They make it back just in time with Kiyomi's help, and River is offended to see her confetti cannons being used by the Hall Moanitors to complete Revenant's master plan. She then assists Kiyomi in sending the Hall Moanitors back to Haunted High, where her skiff is tied up in chains by Revenant after Revenant reveals herself to be the Red Lady of ghost legend. After Revenant realizes her error and asks for forgiveness as she repents and promises to get rid of her chains through honest means from now on, River lends her skiff to the celebration that follows to celebrate the new-found friendship between Monster High and Haunted High. As an added bonus, while River works the DJ station with Holt Hyde, the Hall Moanitors are punished with swabbing the deck of River's skiff in retaliation for what they did to her confetti cannons earlier. Haunted