Jenkins is the janitor at P.S. 38. He may be Jenny's father as their last names are both Jenkins.
Enemy is in Dr. Cesspool, a comic drawn by Nate Wright. Enemy plays the role as Cesspool's rival. According to Cesspool, Enemy gets to do all the important operations, while all Cesspool does is extract excess earwax.
Nancy was Nate Wright's preschool teacher. Nate remembers her for having "wicked body odor" and her daily sing-alongs. Ms. Nancy has only appeared in Big Nate Lives It up as a flashback sequence.
Stan (P.S. 38 student)
Stan went out with Michelle ever since she told him that she likes him.