As soon as the movie opens you realize you’re back in the classic Bruce Timm “Batman the Animated Series” world, which is a very good thing. Then you see that this particular story is actually a little more adult with actual death, more intense violence, and some adult situations/language; so far so good. Then you realize that for every moment of serious action there is another moment of absurd, slapstick humor and the wheels fall off.
The movie starts out strong enough with both the original Batman and Robin/Nightwing voice actors returning while Melissa Rauch does a pretty decent job as Harley.
Unfortunately once Harley shows up the movie quickly devolves into sex jokes, fart jokes, and general goofball activity. While I don’t have a problem with a goofy/silly story ( there’s a handful of Teen Titans Go episodes I really like) but it’s really jarring when you place it in the classic Bruce Timm Batman world that is known for more mature themes.
The movie really should have been called “Harley Quinn featuring Batman and maybe Nightwing” as they are certainly secondary characters after she arrives. Before I even saw the movie it was pretty obvious that this was just an attempt by DC and Warner Brothers to cash in on Harley Quinn’s huge popularity. As long as it was well executed I personally didn’t have a problem with that. Unfortunately it really wasn’t.