There is a plethora of problematic leading ladies in literature, but one notorious trope that goes back further than Shakespeare is the Manic Pixie Dream Girl. What exactly is a Manic Pixie Dream Girl? 

Before film critic Nathan Rabin coined the term, these girls were basically known for being one-dimensional supporting characters that were created for the purpose of helping progress the male protagonist's character development. They were eye candy, to say the least, but to be more specific in accordance with modern MPDGs, they are quirky, broken, but always very "cool." They're free-spirited, pretty, but not intimidatingly sexy and knowledgeable. They impart to the male character an insight and inspire them. They are white noise and around for the sake of aesthetics. 

So how can you tell if your character is an MPDG? We'll have to take a look back at both modern literature and classic literature to compare and contrast. 

Let’s dissect Calypso from The Odyssey by Homer. For those unfamiliar, this work chronicles the story of a Greek general named Odysseus after the fall of Troy. The Odyssey was composed around the 8th century B.C. So who was Calypso? Beats me! Though, in all seriousness, Calypso was a goddess, a nymph. It should go without saying that nymphomania is correlated to how Greek folklore depicted nymphs like Calypso. Her only real role in Odysseus’s story is that she takes him into her island and blissfully uses him as her boy toy until he realizes, “life’s sweetness [was] ebbing from him in longing for his home,” meaning home is where your heart is (his home, in this instance, was where his wife and son were). It took him ten years to get through perilous journey of tragedy and knowledge, but seven of those ten years were spent with one-dimensional Calypso. Let’s simplify this: Calypso - a sensual goddess, purely there as eye candy, and to help Odysseus develop as a character. If that wasn’t clear enough we could move onto Beatrice from The Divine Comedy or tragic Ophelia, but I want to move closer to the modern day. 

Looking for Alaska by John Green. For starters, I love all the stories I’ve mentioned and admire their respective authors, but it is hard not to just say it. Alaska Young is the ultimate Manic Pixie Dream Girl. Spoilers ahead. Looking for Alaska tells the story of Miles “Pudge” Halter, a watered down Holden Caulfield. He meets Alaska, a cool girl with a quirky name who has quirky hobbies; pulling pranks, and constantly wondering how to get out of her labyrinth of suffering. Alaska dies and her death is the catalyst of Pudge trying to figure out his life for the rest of the year. He obsesses over her death, but ultimately he comes to terms with it and becomes a better person for it. I’ve simplified her whole existence, but it's in the title. She was, like Calypso, eye candy and ultimately existed to move Pudge’s plot along and, in a sense, one could argue this is why the novel is great, but I’m not here to praise the writing, I’m here to expose and explain how you can avoid writing a Manic Pixie Dream Girl, unless of course, that’s what you want. 

So here’s a checklist, if you score higher than a 4 you might have some revising to do: 

1. Does this girl have a unique name? (Spelling counts, i.e. Daisy to Daisie) 
2. Are her quirks what define her? (i.e. when readers read about said character will they see a fully-fledged character or a fully-fledged idea?)
3. Are her quirks eccentric? 
4. What is her ultimate purpose? (Is she there to be a leading lady or is she there to be the lead character’s motivation?) 
5. Is she like other girls? Does she try not to be (that’s okay, don’t worry)? Or is she noticeably unique with ease? (This is a red flag). 

It is absolutely acceptable that they exist purely as a love interest, but they shouldn’t be the catalyst for your main character’s development. Keep these questions in mind when forming your female characters. It is easy to avoid these tropes when your female character isn’t your protagonist. Which begs the question: what if my main character is a woman, how can I tell if she’s an MPDG? 

Just take out question 4, apply the same rules. If you find that your main character is an MPDG then revise, but that’s up to you as the writer. Sometimes it works, but most of the time you end up with a Mary Sue, or the mythical “cool girl.”