Learn German: Mir ist die Schüssel leider heruntergefallen.

Using the dative pronoun Mir with an independent action (like herunterfallen, to fall down) is the standard way to express an accident in German. It translates literally to "The bowl fell down affecting me." While Ich habe die Schüssel fallengelassen is grammatically correct, using this "free dative" structure sounds much more natural for an involuntary mishap because it emphasizes that you didn't do it on purpose.

If the English translation is "I dropped the bowl," why is die Schüssel the subject of the German sentence?

English uses an active structure ("I dropped it"), but German often flips this perspective for accidents. Literally, the German sentence says "The bowl fell down." Because the bowl is the thing doing the falling, die Schüssel is the subject in the nominative case. You (Mir) are placed in the dative case to show you were the bystander negatively affected by the event.

Why is the auxiliary verb ist used here instead of hat?

The main verb is herunterfallen (to fall down). Because falling describes a physical motion and a change of state, it requires the auxiliary verb sein to form the perfect tense. Since die Schüssel is the third-person singular subject, the auxiliary verb becomes ist.

Why is the prefix herunter- necessary? Could I just say Mir ist die Schüssel gefallen?