Opening the Nightosphere

Marceline states that she's not interested in seeing her dad after he had eaten her fries, and rambles on about the method of opening the path to the Nightosphere. Unbeknownst to her, however, Finn is following the method step-by-step, and her ramblings accidentally open up the Nightosphere, setting Hunson Abadeer free into Ooo.

Example of:
Accidental Incantation