Mr. Black is a secret government agent that works with Mr. White and the General. Mr. Black and Mr. White are always at the Tests' house getting Susan and Mary to build them new inventions. He is voiced by Bill Mondy.
Mr. Black, like his partner, is a mutant (Johnny X). His powers include things such as an ability to shoot ropes out of his hands. It is unknown how he can shoot them, but it seems that they shoot out, when he flicks his wrist (this is a reference to the method Spiderman uses to shoot webs from his hands).
Mr. Black wears a black suit with a white dress shirt underneath, along with a black tie. He also wears black sunglasses matching the stereotypical government agent. He is of the Caucasian race and has white hair and a defined jaw. He can sometimes be seen wearing an earpiece, further symbolizing his occupation as a government agent.
Mr. Black is Mr. White's best friend and partner. Even through thick and thin, they always try to make up with each other, and always remain close friends.
Like his friend, Mr. White, he buff and tough federal agent. Mr. Black and Mr. White work for the SSGA (Super Secret Government Agency). But their big secret is that they realize that Johnny and Dukey, along with the girls, are far more capable of crushing any evil that foists itself on Porkbelly than they are. A quid-pro-quo friendship underlies all the madness, and the six actually have fun together.
Although neither of them are very good at their jobs, Mr. Black is often shown to be the more bumbling and easy going of the two. A good example of this is in their debut episode Johnny X. Here he accidently reveals their mutant powers in a very bumbling manner, than just says "Oops", unlike Mr. White who goes crazy and tries to cover it up. This is also shown by the fact that he's an awful dancer, and is usually the first of them to crack a joke. Also when he and he partner are trying to tight rope walk he doesn't want there to be net.
In "Johnny Test in Black & White" when Johnny and Dukey go into his stomach it is clear that Mr. Black likes to eat junk food. He likes to drink lemonade when its a hot day and he likes to dance, though he's horrible. He and Mr. White are also shown to like cooking (like the General).
- He has white skin and white hair, which is ironic since his name is Mr. Black.
- In his debut, he was an enemy of the Tests but quickly became a good friend.
- Memnock, a character from Scott Fellow's newest cartoon, Supernoobs has many things in common with Mr Black and is possibly inspired by Mr Black. Both characters love cooking, hang out with another agent, work under orders from a general, and both characters are voiced by Bill Mondy.