Frasier

After his gun goes off, damaging a tile above the fireplace, Martin tells Niles to get him some spackle. After running around aimlessly for a moment, Niles finally asks Martin, "What's spackle?". Niles should know. In Season 10's "The Harassed", he complains that the remodeling of his office has caused his spackle allergy to act up.

It seems highly unlikely that a veteran cop like Martin would keep a loaded gun in the house, even in a hidden place. Keeping ammunition separate from the weapon in the home is one of the very first rules of gun safety.

Daphne tosses Niles a banana which he fumbles, knocking a shoe box to the floor which contains his father's gun. You can see David Hyde Pierce desperately trying to grab the banana as he needs it for his next line, but when the gun fires, he jumps back, losing the banana in the process. In the very next scene, however, Niles is holding the banana as he says, "I think the banana went off!"

In all episodes following this one, the replaced tile over the fireplace (broken by the bullet accidentally fired from Martin's gun) can be seen to be a shade darker than all the others.