The amorphous creature is a common trope in science fiction.

Mutant (fictional), a common trope in science fiction and comic books.

The concept of a mutant is a common trope in comic books and science fiction.

A common trope is that the ability to work magic is innate and rare.

This is a common trope in Arabic public rhetoric.

A more common trope is the cap of invisibility.

Hanna-Barbera was notorious for using common tropes in its series.

Fable stories were a common trope in medieval and renaissance literature.

The symbols on the flag were common tropes of industry, manufacturing, and agriculture during the mid-20th century.

I'm glad to discover another common trope in this short extract: