Mrs. Franklin is Keesha's paternal grandmother and primary caretaker, voiced by the late Eartha Kitt.
She attended Ms. Frizzle's parent-teacher conference which included a field trip to an abandoned castle. During the visit which focused on bats, she was particularly excited to see bat babies - and noted she didn't know bats took care of their young. She added that she'd recognize the sound of "her Keesha's voice anywhere". During the trip, Keesha became slightly worried that Ms. Frizzle was trying to turn her grandmother into a bat. ("Going Batty")