Which fallacy involves inserting personalities inappropriately into an argument?

The correct answer is personalization.

This is a type of fallacy where you involve somebody's personality into an argument, even though it is completely unnecessary or wrong to do that. For example, if you are going to a dinner party and you are late, and the dinner is overcooked (completely unrelated to you being late), you might start thinking that it happened because of your tardiness, whereas that is obviously not the case.