Diesel dreams of being a PJ Mask hero and uses Ryan's new invention, the PJ Mask Maker, to do so. But Romeo, Night Ninja and Luna Girl learn about the device and it's up to Diesel as Firefly, Gekko, Catboy and Owlette to protect it.
The film starts with Thomas running from Night Ninja and Luna Girl. Crash tells Thomas to get to safety while Ryan and the PJ Masks fight. Crash puts Twilight's crown on Ryan's head and he turned into a demon to fight the two Nighttime villains but he and the PJ Masks are easily outsmarted. As Night Ninja and Luna Girl fist-pump, a young boy with spikey-pink hair, a black costume with aqua-green lines and green and pink eye-wear appears. He fights Night Ninja and Luna Girl and easily defeats them. The young hero calls himself Firefly, whom has the identity of the diesel shunter Diesel during the day.