According to Jimmy, the SoDoSoPa Ninjas believe in something greater than themselves, the ninja warrior's code, and that by following a strict warrior code and staying united, they can defeat all enemies.
The SoDoSoPa Ninjas were originally formed by Token and Kenny (and later Clyde and Davíd) as a way to keep all of the homeless addicts out of SoDoSoPa and away from Kenny's house. They turned SoDoSoPa into a ninja fortress, and wore ninja garb with a face cover. However, their al- black costumes with face coverings combined with their black ninja banners with white Japanese characters give people the false impression that they are supporters of the terrorist group, ISIS. This causes people to flee in terror, making the boys think they are in fear of their ninja abilities.
The main purpose of the SoDoSoPa Ninjas was to keep all intruders out of SoDoSoPa. To this end, they created with a series of childish traps and obstacles, as well as a training area with numerous ropes for swinging and climbing. Numerous shuriken can be seen in wall targets, as well as several training dummies with sticks and spears poking through them. When Cartman and Butters find out about the SoDoSoPa Ninjas, they seek out Stan and Kyle to go with them to make fun Kenny and Token, with Cartman, repeated claiming "ninjas are gay."(meaning stupid) However, when a couple flees upon seeing the ninjas, thinking them to be terrorists, the boys immediately want to join.
After they are confronted by Officer Barbrady, who accidentally shoots Davíd, it is finally discovered that the boys are ninjas, not Islamic terrorists. Soon after, the City Council makes a deal with the police to turn a blind eye to further police brutality as long the police only brutalized the homeless. Since the police have returned to work and have free reign to harass the homeless, it is presumed the SoDoSoPa Ninjas have disbanded, because both of the lack of need to defend against the homeless addicts and because "ninjas are gay".
While most of the SoDoSoPa Ninjas dress in typical black ninja costumes with a colored armband to signify rank, some of the ninjas can clearly be seen trying to pass off other costumes instead, most notably Kyle who is seen wearing part of a Batman costume.
Butters has his neck brace over the costume.
At their peak, the SoDoSoPa Ninjas consisted of Token, Kenny, Davíd, Clyde, Stan, Kyle, Cartman, Butters, and Jimmy. Timmy was planned to be in the gang too, but ultimately hit the cutting room floor.