Expository excuses

An expository excuse is a trope of TV writing that has been used so many times, lazy writers assume that no one will mind seeing it again.
Noted expository excuses include:
*The surprise confession on the witness stand
*The dramatic revelation of crucial evidence
*The surprise return of a character who was assumed to have already left for the airport, never to see his/her true love again
*The last-minute destruction of evidence needed to clear a character's name or prove they were right in their belief of some fantastic phenomenon.
*The arrival of the police to arrest and/or kill a villain just as he is about to attack the hero or heroine.
*The million-to-one shot that wins the big game.
*The parent-child talk that imparts a valuable life lesson and makes everything OK in the end.
*The retainer's convenient death by ritual suicide to protect the honor of his master. (May only apply to Japanese TV.)