He is the supervisor of Homer at the Springfield Nuclear Power Plant. He appears to have brown skin and blond hair. He seems to really have it in for Homer, due to his incompetence. After Homer collides with a pipe from the reactor while riding in a go-cart, he fires him but he was later reinstated by Mr. Burns and promotes him into safety inspector.
After many seasons since Season 1, his character design has changed dramatically.
In The Simpsons Game, Sherri and Terri blame Kent Brockman for the fact that their parents weren't together anymore, and that Barry Mackleberry had a crush on Brockman. However, little evidence of this is shown in the series. This, therefore, should be considered non-canon.
Unlike his daughters who are a pale shade of yellow or a whitish cream color, he is a decent shade of yellow. He also has naturally blond hair, and wears a tie and jeans.
- Sherri and Terri's last name was finally revealed in "Yellow Subterfuge", written on Principal Skinner's list of students. Therefore, not only their mother and father's last name is also Mackleberry, but their first names have finally been mentioned.
- During Treehouse of Horror XXVII's "BFF R.I.P.", his name is mentioned to be Barry Mackleberry, but just like everything on the Treehouse of Horror universe, this information is considered to be non-canon. However, Barry is indeed Mr. Mackleberry's first name.
- In the FXX Simpsons World script view for "The Daughter Also Rises", Sherri and Terri's mother's first name is Jerri.
- He was a Pilgrim in Thanksgiving of Horror.