The actress feels there is a lot that can be explored in the characters and the relationship between them, according to The Hollywood Reporter.
"There's just so much more to do," she told Tipsy Talk about her role as Harley and Jared Leto's work as Joker.
The movie was critically panned but is doing good business at the box office. The critics were upset that Leto's Joker had little screen time despite being a highlight in the trailers.
Robbie's wish may come true as there are reports that Warner Bros is developing a spinoff of Harley Quinn and several other DC female heroes.