Gorilla Grodd is leading an army to invade the United Nations, so Stargirl, Batman, and Superman are sent to stop him. What should be a relatively simple mission quickly becomes complicated when Mr. Mxyzptlk appears and starts swapping the League member's bodies.
Tropes:
- Amusing Injuries: Superman in Batman's body, starting with slamming himself into the ground trying to fly and going on from there. He even gets classic Ash Face at one point.
- Batman Gambit: Professor Stein provokes Mr. Mxyzptlk by effectively psychoanalyzing him using complex terms, so that he can slip in his reversed name for Mxyzptlk to say out loud without realizing it until it's too late.
- Butt-Monkey: Superman is completely ineffectual while trapped in Batman's body. He doesn't know how to use any of Batman's gadgets and keeps hurting himself due to being unfamiliar with a normal human's limitations.
- "Freaky Friday" Flip: Mr. Mxyzptlk uses his powers to make the Justice League members swap bodies. Stargirl ends up in Superman's body, Superman ends up in Batman's body, and Batman ends up in Stargirl's body. Then more Leaguers arrive and are subjected to the same: Flash and Zatanna swap bodies, Shazam ends up in Plastic Man, who ends up in Cyborg, Ronnie ends up in Shazam, Martian Manhunter ends up in Firestorm, and Dr. Stein ends up in Mxyzptlk.
- Hoist Hero over Head: A gorilla lifts a distracted Stargirl above his head.
- I Meant to Do That: When calling the League for support, Stargirl specifically requests that Firestorm join them. Batman assumes she does so knowing that Firestorm's dual personality, Dr. Stein, will escape into Mr. Mxyzptlk when he does another "Freaky Friday" Flip on the backup team. Stargirl only asks for Firestorm because she wants to meet him and doesn't really have a plan, but she doesn't bother correcting Batman.
- Insistent Terminology: Mr. Mxyzptlk is very insistent that he doesn't cause chaos. He causes mischief.
- Mythology Gag: After the "Freaky Friday" Flip occurs, Grodd quips that the Justice League is having an Identity Crisis.
- Power Incontinence: The body-swapped League members have little to no control over their new bodies and powers. Batman is the sole exception, quickly adjusting to Stargirl's power-set and actually becoming more effective when combining it with his hand-to-hand combat skills.
- Reset Button: Once Mr. Mxyzptlk is banished, his body-swapping shenanigans are undone.
- Sesquipedalian Loquaciousness: How Professor Stein tricks Mxyzptlk into saying his name backwards. He names a bunch of psychological disorders and phobias with multiple syllables, suggesting the imp suffers from them and throws Kltpzyxm in amongst them so when Mxyzptlk angrily repeats Stein to refute him... *poof*
- Vocal Dissonance: Since the League members retain their voices after being body swapped, Batman still has his deep voice while in the body of Stargirl, a teenager.
- Voices Are Mental: The League members retain their voices even after having their bodies swapped. This leads to some Vocal Dissonance, with Batman's deep voice coming out of Stargirl's body and Stargirl's teenage voice coming out of Superman's body.
