When Homer bowls a Perfect Game, the Bowlerama Employees both take out keys to unlock the button that releases the Balloon. But the keyholes are too close together. Double Key systems are supposed to ensure that it is impossible for one person to carry out the action, so the keyholes should be much further apart.
Incorrectly regarded as goofs
"In one episode they say this, but then in another episode they say that, and in yet another episode they say the other." As this is an animated comedy series, the emphasis is clearly on laughs rather than complete verisimilitude. Efforts are certainly made to create a vaguely consistent setting in which mostly consistent characters live and work, and many episodes refer to each other, but rigid consistency of every single detail in all episodes is unnecessary. In many episodes, the fact that something is inconsistent is the express point of a gag. Our general rule is that each episode is expected to be consistent within itself, but intra-episode inconsistencies are not being listed. There can be exceptions for unusually noteworthy matters, e.g., inconsistencies repeated in multiple episodes (such as the hair and skin colors of secondary characters, and the layouts of the main landmarks), drastic changes to a character's nature (such as Ralphie's school status, Jasper's abilities, or Milhouse's hair color), or something with an interesting anecdote behind it (such as Smithers' skin color).