El muggle aparece justo cuando llegamos.

Justo cuando means right when, just when, or exactly when.

So:

• cuando llegamos = when we arrive
• justo cuando llegamos = right when we arrive

It adds a sense of precise timing, often with a slightly dramatic or annoying feel, depending on context.

Because cuando can take either the indicative or the subjunctive, depending on the meaning.

Here, llegamos is indicative, which is used when the action is presented as:

• a fact,
• something habitual,
• or part of a general statement.

So El muggle aparece justo cuando llegamos sounds like:

• The muggle shows up right when we arrive
• a repeated pattern, or
• a vivid present-time statement.

If you were talking about a future event that has not happened yet, Spanish would normally use the subjunctive:

• El muggle aparecerá justo cuando lleguemos.
  = The muggle will appear right when we arrive.

Yes. For many -ar verbs, the 1st person plural form is the same in the present and the preterite.

So llegamos can mean either:

• we arrive
• we arrived

Context tells you which one it is.

In this sentence, because the main verb is aparece in the present, the most natural reading is present/habitual:

• The muggle appears right when we arrive

If you wanted a clearly past version, you would usually also make the first verb past:

• El muggle apareció justo cuando llegamos.
  = The muggle appeared right when we arrived.

Aparece is the 3rd person singular present of aparecer.

The present tense here can be used for a few reasons:

1. Habitual meaning
   It can describe something that tends to happen:

   • The muggle shows up right when we arrive.

2. Narrative or vivid present
   Spanish often uses the present to make a scene feel immediate and lively.

So even if English might sometimes choose a different tense depending on context, the Spanish present is very natural here.

Because Spanish often leaves out subject pronouns when they are already clear from the verb ending.

• llegamos already tells you the subject is we
• so nosotros is usually unnecessary

The full version cuando nosotros llegamos is possible, but it would normally add emphasis, contrast, or clarity.

For example:

• cuando llegamos = neutral, natural
• cuando nosotros llegamos = more emphatic, like when we arrive

Muggle is used in Spanish as a borrowed word from the Harry Potter universe, so it often stays as muggle.

As for el:

1. El means the, so the sentence is talking about a specific muggle, or one already understood from context.
2. The noun is being treated as masculine here, so it takes el.

In practice, with person nouns like this, speakers may choose the article according to the person’s gender or according to established usage. So you may see:

• el muggle
• la muggle

But in your sentence, el muggle is simply the muggle.

All three can fit, depending on context.

Aparecer literally means to appear, but when talking about a person arriving unexpectedly or suddenly, English often sounds more natural with:

• show up
• turn up

So this sentence could be understood as:

• The muggle appears right when we arrive
• The muggle shows up right when we arrive

If the tone is casual, shows up is often the most natural English equivalent.

Yes. Spanish is more flexible with word order than English.

Your sentence:

• El muggle aparece justo cuando llegamos.

A very natural alternative is:

• Justo cuando llegamos, aparece el muggle.

Both mean basically the same thing. The difference is emphasis:

• El muggle aparece... starts by focusing on the muggle
• Justo cuando llegamos... starts by focusing on the timing

Notice that when the cuando clause comes first, a comma is more natural:

• Justo cuando llegamos, aparece el muggle.

When it comes after the main clause, no comma is normally needed:

• El muggle aparece justo cuando llegamos.