A dialogue bubble in a comic strip that serves less as a medium for conversation or character development and more for the purposes of explaining to the reader what they are to find amusing. It is similar to the idea of "telegraphing" a joke; however, instead of simply making it obvious that the joke is imminent, a buckleybox analyzes the joke itself in order to inform the reader from where the humor is intended to be derived.
It is often associated with a lack of writing aptitude, in that the writer is unable to artfully craft humor and must, instead, resort to prolonging the punchline to the extent that it is lost in text. In every situation of a buckleybox, it is possible to remove the box entirely while simultaneously improving the quality of the humor.
Three comic panels that set up an obvious sight gag. Buckleybox in the final panel: "Let's see them fuck with me now that I've got a gun with a TRAIN on it!"