What is a Legal Fiction?

Legal fictions are facts or situations assumed or created by courts which are then used to resolve matters before them. Legal fictions are mostly encountered under common law systems. ~ Wikipedia: Legal Fiction

In other words, legal fictions are things assumed to be true by the courts, usually to fill a legal or factual void. Legal fictions may or may not be statutory, and are used when the situation fits the criteria set in the statute or in the precedents.

Whats's a Non Sequitur?

Non Sequiturs, as a literary device, is a comment which is humorous as it is unrelated to the previous statement. See Wikipedia

Non Sequiturs in logic are arguments in which the conclusion does not follow from the premises. See Wikipedia again