Mr. Mackey, Jr. is the elementary school's counselor at South Park Elementary, best known for saying "m'kay" at the end of most of his sentences. He also serves on the City Council as head of Public Health. His first name is unknown.
Mackey is known to have a talent in singing and has sung the following songs:
- In Ike's Wee Wee, he sings the Pat Benatar song Love is a Battlefield, while staggering home drunk.
- In "Mr. Hankey's Christmas Classics," Mackey sings Carol of the Bells.
- In South Park: Bigger, Longer & Uncut, Mackey sings his own song "It's Easy, Mmm'kay" to his students to stop them from swearing.
- In "I'm a Little Bit Country," he sings the episodes final song with other South Park townspeople.
- In "Royal Pudding," he is shown to be in charge of a play for the Kindergartners, involving helping their singing.
Mackey wears a green long-sleeved shirt, blue tie, blue jeans, and blue shoes. His hair is black, and thinning. He wears large, black-rimmed glasses. Mackey is well-known for his exaggeratedly large balloon head. It has been implied in "Ike's Wee Wee" that the size of his head is caused by the tightness of his tie. Yet, in "Child Abduction is Not Funny," his parents are shown to have the same condition. However, in "Proper Condom Use," his tie is removed before he and Ms. Choksondik have intercourse, and his head remains the same size.