The cinematic version of Constantine originally featured Michelle Monaghan in a central role - here's why she was ultimately cut from the majority of the film. The character of John Constantine was created by Alan Moore in collaboration with artists Stephen R. Bissette, John Totleben, and Rick Veitch. Though a background figure in Swamp Thing #25 was retroactively declared to be him, Constantine didn't make his first official debut until Swamp Thing #37. In 1988, he was spun off into his own series: Hellblazer by Jamie Delano and John Ridgway. Visually inspired by Sting, Constantine is characterized as equal parts warlock, occult detective, and con man. He has remained a popular figure ever since.
In 2005, the character made his live-action debut with Keanu Reeves in the titular role. Constantine was the theatrical debut of Hunger Games franchise director Francis Lawrence. The film also starred Rachel Weisz as a grieving police detective Angela Dodson, Shia LaBeouf as a younger version of John's comic book ally Chas Kramer, Tilda Swinton as the archangel Gabriel, and Djimon Hounsou as Papa Midnite. Upon release, the film didn't fare well with critics or audiences. Fans of Hellblazer were particularly aggrieved by the changing of the character's core characteristics. However, in the years since, its cult following has grown, with frequent calls for Reeves to return to the role in a belated sequel.
Reeves, Lawrence, and producer Akiva Goldsman were on hand to celebrate Constantine's 15th anniversary at Comic-Con@Home. Among several other things, they discussed the fact that Monaghan originally had a pivotal role in the film. She would have played Ellie, a half-demon would have been in a relationship with John. As such, she had multiple scenes in the film and would have been a principal ally to him. Despite filming the scenes, they were eventually taken out. Asked specifically about it, Lawrence shed some light on why that particular decision had been made:
"We had real story reasons for doing it. It was not her performance, she's a fantastic actress and we really liked the work that she did. We just decided that Constantine was better alone, and feeling like he didn't have a companion that he could, sort of, lean on and have a relationship with."
Ellie was based on a comic book character created by Garth Ennis and Will Simpson. Known fully as Chantinelle, she was a disgraced succubus who fled Hell and ultimately befriended John. Her journey in the comics is quite a storied one. In fact, one aspect of her tale (the conception of a child with an angel) even served as Ennis' inspiration for creating Preacher. That fact makes it all the more disappointing that she was removed from the movie, and didn't get a second chance to appear in a sequel. However, some of her scenes were included among the deleted scenes on DVD.
In fact, one of Ellie's moments can actually be seen in the theatrical release, when she is caught in the blasts of holy water John unleashes through a sprinkler system. Her character is neither named nor directly addressed. Ironically, Lawrence also stated that the scene and the line she was given was the one scene and line that she hated. Still, there are likely no hard feelings from Monaghan. It was no doubt for the best, with the film best able to get to the core of John Constantine's personality befitting the film's tone and storyline. With that now out of the way and firmly ingrained in fan's minds, there's always a chance she could appear and help open up new facets of the character - should a long-desired Constantine sequel ever actually emerge.