Delia and Deirdre Dennis, collectively known as Dee Dee, are identical twin sisters in the DC Animated Universe, recognized as antagonists within the Batman Beyond storyline. As the granddaughters of Harleen Quinzel, better known as Harley Quinn, they inherited her exceptional acrobatic skills, chaotic disposition, and affinity for criminal antics. Raised by a reformed Harley in an effort to steer them toward a lawful life, the twins nonetheless embraced delinquency, joining the Jokerz gang in a futuristic Gotham City while still in their early teens. They first appeared in the 2000 direct-to-video animated film Batman Beyond: Return of the Joker, establishing themselves as coordinated and formidable henchwomen.
In Batman Beyond: Return of the Joker, Dee Dee served directly under the resurrected Joker, participating in thefts of advanced technology and engaging in intense confrontations with Terry McGinnis, the new Batman. Their Olympic-level gymnastics and synchronized combat tactics allowed them to overwhelm opponents through deception and teamwork, marking them as significant threats. A pivotal development occurred at the film's conclusion, where, following their defeat and arrest, an elderly Harley Quinn bailed them out of jail, scolding them for following in her former criminal footsteps and revealing the strained yet enduring familial bond, as the twins irreverently addressed her as "Nana Harley."
Beyond their debut, Dee Dee featured in the Justice League Unlimited episodes "The Once and Future Thing," with a notable role in an alternate timeline where they were enhanced by Chronos, gaining the ability to duplicate upon impact and wielding energy whips. These upgrades amplified their lethality, enabling them to overpower members of the Justice League. Their character embodies the persistent legacy of Harley Quinn's influence across generations, appearing occasionally in related comic adaptations and reinforcing their status as recurring delinquents in the broader DC Universe.