Disappearium

Disappearium is a Cybertronian element that can render whatever item it is made of invisible, such as Optimus Prime's trailer/Combat Deck when Prime converts to robot mode.

Note

• In the audio commentary for The Transformers: The Movie featuring Flint Dille, Susan Blu, and Nelson Shin, Dille gave a final explanation, during Optimus Prime's final attack against the Decepticons during the Battle of Autobot City, to what happens to Optimus Prime's trailer/Combat Deck when Prime converts to robot mode. According to Dille, the trailer is composed of disappearium, an element that has cloaking properties to it. And if you believe that, can we interest you in a case of dehydrated water?
• In real life, Prime's disappearing trailer/Combat Deck was a simple case of the writers not bothering to work out the minor technical details of a children's cartoon.