When Lord Siva appears to Ravana to grant his wish, Lord Vishnu manipulates Ravana's mind and makes him wish for Goddess Parvathi. As Ravana proceeds home with Goddess Parvathi, Narada meets him midway and tells him that his companion is a fake Parvathi.
When Lord Siva appears before Ravana to fulfill his desire, Lord Vishnu manipulates Ravana's thoughts, causing him to desire Goddess Parvathi. As Ravana journeys home with the supposed goddess, Narada interrupts and reveals that his companion is actually a fake Parvathi.