A feature-length animated film, "DC Super Hero High: Mayhem in Metropolis," pits the lighthearted, comedic style of the DC Super Hero Girls (2019) series against a darker, more serious alternate version of the same characters and their world. The film opens with the familiar, upbeat Super Hero High, showcasing the girls' usual antics and friendships. However, a strange energy surge from a malfunctioning experimental device in the school lab creates a dimensional rift, pulling in an alternate version of Metropolis and its inhabitants.

This alternate Metropolis is grittier and more dangerous. The Super Hero Girls from this dimension are hardened veterans, battle-scarred and cynical, reflecting a world where heroism comes at a much higher cost. Their designs are darker, their personalities more serious and brooding. Wonder Woman is a hardened warrior, less playful and more strategically focused. Supergirl is haunted by past losses and carries a heavier burden of responsibility. Batgirl is a more ruthless detective, operating in the shadows. This alternate team is initially hostile towards their brighter counterparts, viewing their carefree attitude as naive and reckless.

The conflict arises from the clash of these two vastly different interpretations of the same characters. The lighthearted Super Hero Girls struggle to understand the cynicism and severity of their alternate selves, while the hardened veterans see the original team's optimism as a dangerous weakness. The plot revolves around the need to close the dimensional rift before the alternate Metropolis's darkness completely consumes their own world. This requires both teams to overcome their differences and learn from each other.

The humor comes from the juxtaposition of the two styles. The slapstick comedy of the original team clashes with the grim determination of their counterparts, creating humorous misunderstandings and unexpected alliances. For example, a scene could involve the cheerful, bubbly Harley Quinn from the original series attempting to cheer up the brooding, battle-worn Harley Quinn from the alternate dimension, only to be met with a sarcastic retort and a glare. Another scene could involve a training montage where the two Wonder Womans clash in fighting styles, the original's playful acrobatics contrasting with the alternate's brutal efficiency.

The climax involves a combined effort to close the rift, requiring both teams to use their unique strengths. The original team's optimism and teamwork inspire their alternate selves to rediscover hope, while the alternate team's experience and battle-hardened skills provide the necessary tactical edge. The film ends with the rift closed, both teams having learned valuable lessons from each other, and a newfound appreciation for their respective perspectives on heroism. The film subtly explores themes of perspective, the cost of heroism, and the importance of balance between optimism and realism. The post-credit scene could hint at the possibility of future dimensional rifts, setting the stage for a sequel.