A developer builds a spooky Halloween-themed hackpack using Arduino, littleBits, and Laravel to create an interactive display that changes based on incoming SMS messages. The hackpack features two images: a bat and a ghost, which are displayed with blinking eyes. The developer uses PHP in Laravel to communicate with Twilio and the littleBits Cloud API, allowing users to send text messages to update the display. The Arduino code reads input from the cloudBit device and updates the display accordingly. The hackpack is completed by integrating the Laravel backend with the Arduino frontend using the littleBits Cloud API.