Fireballs are combustible projectiles that can be generated from the hands. They are mainly used by Mario, Luigi, Wario, and Waluigi, but other characters, namely Nox Decious and the Darkness, have exhibited the ability to create variants of them, too. Like beam swords, the core of a fireball reflects the user; if the user is pure then the core of their fireball is white and if they are evil the core is black. Fireballs usually are effective against most enemies, but they can be deflected or dissipated using telekinesis.
However, this didn't apply to Wario when he was confused, his fireball cores still appeared to be white, even though the Nether Saber's core was blue, which one could speculate that fireballs tell if you are ultimately good or evil, where there is no in between. Although they are called fireballs, they have never been associated with fire, only exploding when they make contact. When the Energy Source is destroyed, Mario, Luigi, and Wario lose the ability to use fireballs.
Fireballs were later used in a dream sequence in "Death is Like A Box of Chocolates" by Mario and Wario against each other. However, they decided to stop using fireballs and battle with their fists instead. Wario reminds Mario that they lost their powers and Mario awakens from his dream.
The group would later discover that Waluigi still possessed his powers, including his ability to create fireballs. The group would later get their powers back from Waluigi by means of a power transfer, but at the expense of him being put in a year-long coma. Afterwards, Luigi used them against a couple of ninjas in "Plumbers and Ninjas and Snakes OH MY!".
In his battle with Blaire, Waluigi used what appeared to be a super-charged fireball to overpower him.
- Mario has the ability to create super-sized fireballs, but they take time to charge them up.
- Upon becoming Fire Mario, Mario gained the ability to generate fireballs at a much faster pace. This was demonstrated in his battle with Mr. L; as well as the ability to absorb energy blasts and compress them into nothing, before converting the energy into fireballs that he could use.
- Once, Wario and Waluigi combined their fireballs to knock out Luigi in Stupid Smash Brothers.
- In "Bloody Confrontations," Wario and Waluigi created an enormous fireball out of the fireballs that they were firing at each other. But when they got too close, it exploded and knocked them to the ground.
- In Plumber Knight Returns the Blue Hood had a blaster that takes his natural firepower and focuses it into a powerful blast which he used to completely incinerate goombas and Jeckle.
- At the beginning of the series, the fireball launching sound was the same as that used in the Super Mario video games. However, later in the series, when the story got more serious, fireballs made more of a whooshing sound. It then reverted to the original sound in "Act II Part 4" of the film.