An is a reference, usually to literature, but there are many different ways to write with allusions!
You’re so pretty! Even Aphrodite would be jealous! This is an allusion to the Greek Goddess of beauty, Aphrodite.
My daughter’s grades are sinking as badly as the Titanic. This is an allusion to the ship, Titanic.
Stephen A. Hawking is known as the modern Einstein. This is an allusion to Einstein, a brilliant and well-known scientist.
We don’t know who lives in that deserted house. The person who lives there is the Boo Radley of this neighborhood. This is an allusion to a character named Boo Radley in “To Kill a Mockingbird” by Harper Lee, and this character was known for being a mysterious neighborhood legend.