Learn Russian: Актёр спрятался среди поклонников.

The preposition среди (among) always requires the Genitive case. Since the actor is hiding among multiple fans, we use the Genitive plural form of the masculine noun поклонник, adding the standard -ов ending.

Why does the verb спрятался have the reflexive -ся ending?

In Russian, спрятать means to hide an object (like hiding a book or a treasure). Because the actor is hiding himself, you must use the reflexive form спрятаться. Since the actor is masculine and this is the past tense, it becomes спрятался.

Could I use между instead of среди to mean 'among the fans'?

Usually no. While both can translate to 'among', среди is the best choice when someone is surrounded by a larger group or mass, like a crowd. Между focuses more on being positioned 'between' specific, distinct things, and it usually takes the Instrumental case rather than the Genitive.

What is the origin of the word поклонников?

The dictionary form is поклонник (fan or admirer). It comes from the noun поклон (a bow), originally referring to someone who bows down in worship or deep respect. Today it is the standard word for a fan of an artist, but it can also mean a romantic suitor.