Naruto himself is often a main character. Since the 'saimin no jutsu' is part of the Naruto universe, he could be either the caster or the victim of the jutsu. His unique personality and his own jutsu repertoire can interact in interesting ways with the sleeping jutsu.
Obviously Naruto is one of the main characters. And then there are usually some of the female characters from the Naruto series like Sakura, Hinata, and maybe even some of the female ninja from other villages. They are often part of the harem that revolves around Naruto.
It could be a rogue ninja who has mastered a form of anti - Saimin Jutsu. This ninja could be out to prove that Naruto's Saimin Jutsu is not as powerful as everyone thinks and wants to defeat Naruto to gain fame in the ninja world.
Some fanfics might also feature Kakashi. He has knowledge of many jutsu and a past that is filled with secrets. So, he could be the one who either discovers a new aspect of a forbidden jutsu or is trying to prevent others from misusing it.
Naruto himself is often involved. Since he has a strong will, it's interesting to see how he would deal with being possessed or using the possession jutsu. Sasuke is another common character. His dark past and powerful abilities make for great storylines when combined with possession jutsu.
Naruto is almost always the main character in 'Naruto Foodgasm Fanfic'. His love for food is well - known in the original series, so it makes sense. Sometimes his friends like Choji, who also loves food, are involved too.
In addition to the main Naruto crew, characters like Jiraiya can be important in 'prodigious naruto fanfic'. He was Naruto's mentor, so in fanfics that explore Naruto's growth further, Jiraiya is likely to be there. Also, villains like Orochimaru or Pain can be central in some fanfics, especially those that deal with Naruto facing greater threats or trying to redeem the villains.
Another character that can be involved is Kakashi. He might be the one who discovers Naruto has been hypnotized and uses his wisdom and skills to try and reverse it. Also, characters like Sakura could play a role. She may be worried about Naruto and try to help in any way she can, like researching about the hypnosis or providing medical support if needed.
One interesting aspect could be the unique interpretations of the 'saimin no jutsu' (Sleeping Jutsu). Writers might explore how different characters react to being put under this jutsu in ways not shown in the original Naruto series. For example, they could show the internal thoughts of a character who is being hypnotized, which adds depth to the story.
Sakura is another character that can be involved. Her strength and medical ninjutsu skills can be combined with other offensive or defensive jutsus. For instance, fusing her superhuman strength punch with a genjutsu to create a more complex and powerful attack. Her growth as a character throughout the series also gives room for different fusion jutsu ideas in fanfics.
Gaara could also be part of the fanfic. Since he has his own unique abilities related to sand, there could be an interesting interaction between his powers and Naruto's summoned creatures. For example, Naruto could summon a water - based creature and they could team up with Gaara to fight an enemy that is strong against both sand and water.