Where proper noun in All contestants dress as gorillas?

There are no proper nouns in the sentence "All contestants dress as gorillas."

Here's why:

* Proper nouns are specific names of people, places, or things (e.g., John, London, Eiffel Tower).

* The sentence uses general terms: "contestants" and "gorillas". These are common nouns.

Let me know if you have another sentence you'd like to analyze!