The title of a work and its tone do not match.
Do We Have This One?. Needs More Examples One typically expects the title of a work to reflect the content, tone and style of the content of the work in question, whether it's by summarizing the plot (even to the point of giving away the ending), referring obliquely to the plot and theme of the work by way of classical reference or simply being a silly joke that relates to the story in some way. This trope is when this does not happen. Perhaps the work is dark and serious while the title refers to kittens and rainbows (or vice versa). Perhaps it's a Literary Allusion Title, except the allusion in question makes absolutely no sense in the content of the work. And so on.