That’s simple. Every time someone edits this image to add more villains, they edit the previous version. So someone just added that OC early on and then every version since has had it.
Villains, huh? I still don’t get why that OC is here or why he’s holding that anti Spike poster. I know the commissioner did some shady stuff to get his OC mass produced but, if memory serves, the character themself wasn’t evil or anything.
Because new villains are added all the time to either the show or the comics. So people update it. And sometimes people will notice an antagonist that was not included before and also add them in an update.