Corollary:
Sidekick / love interest: You should wear a bulletproof vest today.
Hero: Ehh, It’s just a routine interview with a witness, and besides, it’s too hot out today.
(Hero is shot point-blank in the chest and falls to the ground! Sidekick goes to their side)
Sidekick: Can you hear me? Speak to me!
Hero: (opens eyes, rips open shirt to display vest with embedded bullet) I changed my mind!
If there is a computer password it will be easily guessed because it will violate all the basic rules of password construction and something on the desk will give it away.
“There’s a picture of his cat. What did he say the cat’s name was? Muffin? Maybe the password is Muffin? It is? Great!”
Along the same lines, if there’s a locked door to the Top Secret Laboratory, and the door lock is controlled by a touchpad, the hero will just happen to have an ultra violet flashlight (or something similar) that will reveal the keys that must be pressed to open said lock. And the order of pressing the keys will be easily deduced, because reasons.
Branching off into television…
Whenever something goes wrong during a live broadcast: “That’s live TV!”
When, on a cooking segment, they show the prep, then go to the oven and remove an already-baked version of the dish: “The magic of television!”
mmm