Plot coupon
From Jenny Everywhere Wiki
During their 2019 quest for the Frost King's treasure in Manik, the Retconning Crocodiles, upon wondering how to get through the ice door, bemoaned their lack of a plot coupon or of “the deorum apparatus unde venerunt”. (PROSE: The Frost King's Treasure)
Behind the scenes
A “plot coupon” is a term referring to a plot device which exists as a temporary target which characters need to advance to the next stage of the narrative. The term is often derogatory, implying that the plot point is clumsy and contrived. While TVtropes considers it a trope in its own right, Wikipedia considers the term broadly synonymous with “MacGuffin”.