When a character, who was previously presumed to be organic, is revealed to be a robot all along.

The reveal itself can happen in a number of ways. Examples include:

• Their skin peels off, revealing an endoskeleton or machinery underneath.
• They start babbling incoherently or repeat error messages or random series codes in a robotic voice.
• They start convulsing uncontrollably and sparks of electricity or plumes of smoke start coming out of them.
• A hidden panel, port or slot opens up somewhere on their body.
• Someone peeks inside their bedroom and see them doing repairs on themselves. Parts splayed on a desk with tools.
• A limb falls off from their socket, revealing wires and machinery from the stump.

The Terminator is one such examples of this.