El inodoro se atascó justo antes de que llegaran los invitados.

Because atascarse is very commonly used as a pronominal verb to mean to get clogged / to get blocked / to get jammed.

So:

• atascar = to clog something / to block something
• atascarse = to become clogged / to get blocked

In this sentence, the toilet is not actively clogging something else; it itself became clogged, so se atascó is the natural choice.

Compare:

• Alguien atascó el inodoro. = Someone clogged the toilet.
• El inodoro se atascó. = The toilet got clogged.

That se is not reflexive in the English sense of it clogged itself. It is just part of the verb form learners need to remember here.

Atascó is the preterite of atascarse in the third person singular:

• yo me atasqué
• tú te atascaste
• él/ella/usted se atascó

The preterite is used because this is a completed event in the past: the clog happened at a specific moment before the guests arrived.

So the sentence presents the clogging as a single finished event:

• The toilet got clogged just before the guests arrived.

If you used the imperfect instead, it would sound odd here unless you were describing an ongoing situation rather than a completed event.

Because antes de que is followed by the subjunctive, not the indicative.

So:

• antes de que llegaran = before they arrived

This is a very important pattern in Spanish:

• antes de que + subjunctive

Examples:

• Salí antes de que empezara la película.
• Apaga la luz antes de que te vayas.

You do not say:

• antes de que llegaron ❌

because after antes de que, Spanish treats the following action as something viewed from the perspective of the first action, and that structure requires the subjunctive.

It is in the imperfect subjunctive because the main verb is in the past:

• se atascó = past
• so the verb after antes de que also goes into a past subjunctive form: llegaran

This is part of normal sequence-of-tenses behavior in Spanish.

A very useful pattern is:

• present/future main verb -> present subjunctive
• past main verb -> imperfect subjunctive

Compare:

• El inodoro se atasca antes de que lleguen los invitados.
  The toilet gets clogged before the guests arrive.

• El inodoro se atascó antes de que llegaran los invitados.
  The toilet got clogged before the guests arrived.

Yes. Llegaran and llegasen are both valid imperfect subjunctive forms.

So both are correct:

• antes de que llegaran los invitados
• antes de que llegasen los invitados

In modern everyday Spanish, especially in speech, the -ra form is generally more common:

• llegaran

The -se form is not wrong at all; it can sound a little more formal or literary depending on context and speaker.

Justo means just in the sense of exactly / right.

So:

• antes de que llegaran los invitados = before the guests arrived
• justo antes de que llegaran los invitados = just before the guests arrived / right before the guests arrived

It adds emphasis and makes the timing feel more precise and dramatic.

Compare:

• Se atascó antes de que llegaran los invitados. = It got clogged before the guests arrived.
• Se atascó justo antes de que llegaran los invitados. = It got clogged right before the guests arrived.

Yes, inodoro is correct and standard, and everyone will understand it. However, in Spain, in everyday speech, people also often say:

• váter
• WC
• sometimes retrete in certain contexts, though this can sound more old-fashioned or specific

So in Spain:

• El inodoro se atascó. = perfectly normal
• El váter se atascó. = also very common and natural in speech

A learner should recognize all of these, but inodoro is a very useful standard word.

Because the full conjunction is antes de que.

You can think of it as a fixed expression meaning before when it introduces a clause with a conjugated verb.

Compare:

• antes de llegar = before arriving
• antes de que llegaran = before they arrived

So:

• antes de + infinitive
• antes de que + subjunctive

Examples:

• Me fui antes de comer.
• Me fui antes de que empezara la cena.

You cannot omit the de here.

Because los invitados is the subject of llegaran, not a direct object.

The personal a in Spanish is used before human direct objects, for example:

• Vi a los invitados. = I saw the guests.

But here, los invitados are the ones doing the arriving:

• llegaran los invitados = the guests arrived

Since they are the subject, not the object, there is no personal a.

Because los invitados refers to a specific group: the invited guests relevant to the situation.

Spanish often uses the article where English might not emphasize it as much. Here, los sounds natural because we are talking about the guests everyone already knows about in the context.

• llegaran los invitados = the guests arrived

If you said just invitados here, it would be ungrammatical in this sentence.

Yes, but it would mean something slightly different.

• El inodoro se atascó = The toilet got clogged.
  This focuses on the event of becoming clogged.

• El inodoro estaba atascado = The toilet was clogged.
  This focuses on the state/condition.

So the original sentence tells us that the clogging happened right before the guests arrived. If you said estaba atascado, you would be describing its condition rather than the moment the problem occurred.

Yes, but the meaning shifts a little.

• se atascó = it got clogged
• se había atascado = it had gotten clogged / it had clogged up

The pluperfect (había + participle) places the clogging even more clearly before another past point.

So:

• El inodoro se atascó justo antes de que llegaran los invitados.
  The toilet got clogged just before the guests arrived.

• El inodoro se había atascado justo antes de que llegaran los invitados.
  The toilet had gotten clogged just before the guests arrived.

Both can work, but the simple preterite is more direct and is very natural here.

The given order is very natural, but Spanish allows some flexibility.

Original:

• El inodoro se atascó justo antes de que llegaran los invitados.

You could also say:

• Justo antes de que llegaran los invitados, el inodoro se atascó.

That version puts more focus on the timing.

Both are correct. The original sounds very natural in ordinary narration, while the fronted version can sound a bit more dramatic or stylistically marked.

Not exactly. Even though the English translation may be arrived, the Spanish form llegaran is grammatically different because it is subjunctive, not a normal past indicative form.

Compare:

• Los invitados llegaron. = The guests arrived.
  This is a straightforward past statement in the indicative.

• antes de que llegaran los invitados = before the guests arrived
  This uses the imperfect subjunctive because the structure requires it.

So in translation they may look similar, but in Spanish the grammar is different.