In the "Jafar's Hour" segment (the one in which he makes his two first wishes and sings his reprise of "Prince Ali") of Disney's Aladdin, Jafar uses his sorcerer powers to reverse Aladdin's clothes from the Prince Ali outfit to the "street-rat" rags, revealing him as Aladdin. But why does Jasmine believe so quickly that Aladdin was a street rat all along disguised as Prince Ali ? Of course, it is the truth, but it's not what a normal person would deduce from the situation.
Remember that at that point, Jasmine has been told by Aladdin-Prince Ali that he actually is Prince Ali but sometimes disguises as Aladdin the Street Rat, an explanation that made sense and convinced Jasmine. Jasmine, when seeing Jafar turning back Ali in his Aladdin clothes, should have normally thought: "This rotten guy is putting Ali back in his disguise to humiliate him ! And he thinks I am going to believe his crazy story that this is his true form ? Bah !".
Of course, unless the writers were dumb (which I refuse to think of the Disney artists), I'm probably missing some detail. If you know what this detail is, may you answer ?