Which packaging innovation, introduced for home video in the early 2000s, featured special ink that revealed hidden movie content when exposed to heat from touch?

Film and television marketing relies heavily on visual packaging to attract audiences. From movie posters to DVD/Blu-ray boxes to streaming thumbnails, the way studios 'package' their content has evolved dramatically over the decades. This trivia question explores an innovative packaging technique that changed how audiences interact with physical media in the entertainment industry.

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Thermochromic DVD cases for 'The Ring' (2002) that revealed a hidden well when warmed
Lenticular Blu-ray sleeves for 'Avatar' (2009) that showed different Pandora landscapes at different angles
Glow-in-the-dark VHS boxes for 'The Blair Witch Project' (1999) that revealed map coordinates
Scratch-off DVD covers for 'The Da Vinci Code' (2006) that unveiled hidden symbols beneath