Has anyone wondered why Shigeo is called "Mob"?...
There are actually a few reasons why Shigeo is called “Mob!”
The reason his friends call him that, most likely, is because the characters in his name ( 茂夫) can also be read as “mobu” ( モブ)! So it’s somewhat of a nickname based on that.
In terms of symbolism, I believe that a “mob character” is essentially a background character: someone who doesn’t stand out. This fits Mob’s theme of not standing out despite his powers!