It doesn't have the power
At the Utonium chateau, the Girls bake the perfect little pie by adding together their own mix of sugar, spice, and everything nice, and Bubbles adds Chemical X to make it super. Then Mojo Jojo decides to steal it and feed it to all of the villains and bullies in Townsville! So then the Girls must fight every bad guy in Townsville and retrieve all of the Chemical X before it's too late.
The game plays like the Capcom fighting game Power Stone, where you play as one of the girls and use punches, kicks, and throwing projectiles against your opponent. The aim is to deplete your opponent before they do, in a best of two-out-of-three battle. The game plays identically to another fighting game from the same developer called Tom & Jerry: Fists of Furry, making it nothing more than a reskin of that title.
The gameplay is nothing but repetitive: All the girls play exactly the same as each other, with no differences between them at all. Even the villains all play similar to each other as well with no difference in moves or gameplay. The stages are also incredibly small and are just the same arena just with a different backdrop to represent the place where the villain is battled.
It's impossible to unlock everything in the game. Although each Powerpuff Girl can unlock something (e.g., a villain to play as, or a stage) but once you defeat Mojo Jojo, you can't replay it again.
The game can be beaten in less than an hour if the player is experienced enough.
The Multiplayer mode is also very lacking and has a strange character limitation. You can't fight as two of the girls, you can only fight as a Girl vs. Villain, or a Villain vs. Villain.
For some weird reason, the true ending is with Blossom.
Since there are no cutscenes (due to the N64 cartridge limitations), the story is just told through text, which is very hard to read due to the font used, and it's not really explained well (eg, Bubbles is the one who suggests putting Chemical X into the pie in the PS1 version, yet in this version, it says that all the Girls chose to add it in.)
There is no voice acting. The only dialogue that plays throughout the whole game is random "Oof!"'s and "Ow!"'s that sound like they were recorded by random people.
Only one piece of music plays throughout the game, making it very annoying.
The Girls have an explosion attack that makes the battles way too easy.
Unlike the PlayStation version, you have to rely on passwords to continue playing.
It was released very late into the N64's life, as the GameCube had just come out a while before, which is a bad sign.
Overall, the N64 version has no power.