Learn Farsi: اگر آن کمدین تپق نزده بود، حضار نرفته بودند. - If that comedian had not fluffed his lines, the audience would not have left.

This is a past unreal conditional (talking about a situation that didn't actually happen in the past). In English, we mix structures: "If X had happened, Y would have happened." But in Farsi, the rule is much simpler: just use the past perfect tense in both the "if" clause and the result clause.

We have been focusing on the subjunctive in this lesson. Why is there no subjunctive verb here after اگر (if)?

While اگر often triggers the subjunctive for present or future possibilities (e.g., "if he plays..."), it does not for impossible past situations. Because the comedian's performance is already over and the condition can no longer be met, Farsi drops the subjunctive and uses the past perfect (نزده بود) instead.

What exactly is the phrase تپق زدن?

تپق زدن is an essential idiom for intermediate learners. It means to stumble over your words, make a slip of the tongue, or fluff your lines. Historically, it referred to a horse stumbling, but today it is almost exclusively used for speaking mistakes.

The English translation says "the audience", which is a collective noun. Why does it take the plural verb نرفته بودند?

The word for audience here is حضار. This is an Arabic "broken plural" of the word حاضر (meaning "present" or "attendee"). Because حضار literally means "those present" or "the attendees", it functions as a regular plural noun in Farsi and requires a plural verb.