Once Upon a Time and Frozen: It’s a match made in fairy tale (and corporate synergy) heaven. But how did this chocolate-and-peanut butter pairing come about? What was the moment of inspiration when ABC’s Once Upon showrunners Edward Kitsis and Adam Horowitz decided to take on the biggest animated movie in history for a story arc this fall during their hit show’s fourth season? As it turns out, the precise moment was captured on camera in the Once Upon writers room. The team revealed the footage to fans during the Once Upon panel at Comic-Con on Saturday. We have the clip for you now, exclusively on EW.com. Enjoy this (rather hilarious) scene of behind-the-scenes creative illumination: