Learn Hardcore German: Irgendwann abends ruft sie mich an und erzählt etwas Lustiges. - Sometime in the evening she calls me and tells me something funny.

German main clauses are verb-second (V2). Because the time phrase Irgendwann abends is placed at the start (the “prefield”), the finite verb (ruft) must be in second position, and the subject (sie) moves after it: Irgendwann abends | ruft | sie | mich an …

Why is an at the end of ruft … an?

Anrufen is a separable-prefix verb. In main clauses the prefix splits off and goes to the end: sie ruft mich an. In a subordinate clause or with a participle, the prefix stays attached:

…, dass sie mich anruft.
Sie hat mich angerufen.

Why is it mich and not mir?

Because anrufen takes a direct object in the accusative: jemanden anrufen. So it must be mich (accusative), not mir (dative).

Correct: Sie ruft mich an.
Wrong: Sie ruft mir an.

Does erzählen need a dative person (like “tell me”) here?

It doesn’t have to be stated, but it can be. Erzählen often takes two objects: dative for the person and accusative for the thing told.

With dative made explicit: … und erzählt mir etwas Lustiges.
Without dative (listener understood from context): … und erzählt etwas Lustiges.

Why is there no comma before und?

In simple coordination with und, German normally does not use a comma. Your sentence is a straightforward coordination of two predicates, so no comma is needed.

Can/should I repeat the subject after und?

You can, but you don’t have to. German allows you to omit a repeated subject in coordinated clauses (this is called “gapping”).

Both fine: … ruft sie mich an und sie erzählt … / … ruft sie mich an und erzählt … The version without the second sie is more natural here.

What exactly is going on with etwas Lustiges (capital letter and -es ending)?

Lustiges is a nominalized adjective (an adjective used as a noun), so it’s capitalized.
After etwas (and similar words like nichts, viel, wenig), the adjective takes strong neuter singular endings. In accusative (and nominative) neuter singular, that ending is -es: etwas Lustiges = “something funny.”
More examples: nichts Gutes, viel Interessantes, wenig Neues.

Is lowercase etwas lustiges acceptable?

No, standard orthography requires capitalization when an adjective is used as a noun: etwas Lustiges.

Could I say irgendwas Lustiges or was Lustiges?

Yes. Irgendwas and was are colloquial variants of irgendetwas and etwas. All are common:

Neutral/standard: etwas Lustiges, irgendetwas Lustiges
Colloquial: was Lustiges, irgendwas Lustiges

Do I need von/über with erzählen?

Only if you want to specify the topic with a preposition:

Direct object (what is told): Sie erzählt mir eine Geschichte.
Topic with von/über: Sie erzählt von ihrem Tag. / Sie erzählt über ihre Reise.
In your sentence, erzählt etwas Lustiges uses a direct object; no preposition is needed.

What’s the difference between abends, am Abend, and expressions like heute Abend?

abends = in the evening(s) (adverb). It can be generic/habitual or just mean “at some point in the evening” depending on context.
am Abend = in the evening (prepositional phrase; a bit more specific/formal).
heute Abend = this evening (definite time today).
Your irgendwann abends means “sometime in the evening,” with the time left vague. Irgendwann am Abend is very similar in meaning.

Why does abends end in -s? Is that a genitive?

No, it’s not genitive. German has adverbial time-of-day forms ending in -s: morgens, vormittags, mittags, nachmittags, abends, nachts. They mean “in the morning/…/in the evening/at night.”

Can I move the time phrase to the middle? What’s the natural word order?

Yes. Time phrases are flexible. Common patterns:

Fronted for emphasis: Irgendwann abends ruft sie mich an …
Midfield: Sie ruft mich irgendwann abends an …
A good default is Time–Manner–Place. With multiple time elements, German often goes from general to specific; both irgendwann abends and abends irgendwann are possible, with slight rhythmic/emphasis differences.

Where do pronouns go with separable verbs like anrufen?

Personal pronouns tend to come early in the midfield, before the separable prefix at the end:

Natural: Sie ruft mich heute Abend an.
Odd/stressed: Sie ruft heute Abend mich an. (possible only for special emphasis) You can’t place mich after an; the prefix must be the last element of the clause.

Is anrufen the only way to say “call”? How is it different from rufen and telefonieren?

anrufen + Akk. = call (by phone): Sie ruft mich an.
telefonieren (mit + Dat.) = talk on the phone (intransitive): Sie telefoniert mit mir.
rufen + Akk. = call/shout to someone: Sie ruft meinen Namen.
Also useful: zurückrufen (to call back), durchrufen (to give a quick call).

What does the present tense here mean—habitual, future, or a single event?

German Präsens is flexible. Depending on context it can mean:

Habitual: “She calls me (at some point) in the evenings …”
A single event told in the “narrative present.”
Near-future if made clear by context: Heute Abend ruft sie mich (irgendwann) an.
For explicit future you can also use werden: Sie wird mich heute Abend anrufen. For past: Sie hat mich abends angerufen / Sie rief mich abends an.

Could sie mean “they” or formal Sie here?

No. The verb form ruft is 3rd person singular, so sie here = “she.”

“they” would be sie rufen.
Formal “you” would be Sie rufen (capital S and plural verb form).