Quinn's stock is rising thanks in part to keen anticipation of the 2016 film "Suicide Squad," which will star Australian actor Margot Robbie as Quinn along with Jared Leto and Will Smith.
"Harley Quinn" was the most-searched term in relation to Halloween costumes across the United States, according to Google's Frightgeist, a tool that tracks top queries on the search engine.
The Quinn searches were especially popular in cities including Houston, Philadelphia and Seattle, according to the data by Frightgeist.
On Twitter, hashtags including #SuicideSquadHalloween #HarleyQuinn, #SuicideSquad were actively trending on Friday.
Other characters including Batman and Joker from "Suicide Squad" - a film about imprisoned supervillains executing dangerous black ops missions in exchange for clemency - were among the top 10 costume searches on Google. Other popular costumes were Minnie Mouse, Wonder Woman, and characters from the movies "Star Wars" and "Minions."
Republican presidential candidate Donald Trump was the only politician to show up on the Frightgeist list of popular costume searches. The celebrity real estate tycoon ranked No. 105 nationwide.
Harley Quinn costumes sold for $52-$55 on average at online retailers including PartyCity.com and BuyCostumes.com. A recent report by the National Retail Federation estimated total Halloween spending in 2015 to top $6.9 billion, with the average American planning to spend $74.34 on decorations, candy, costumes and more.