Gerry's day is ruined when his mouthy and least favourite student is Principal for a Day. Meanwhile, a harmless prank on Lisa takes a horrific turn; and Bobbi's well-intentioned meddling accidentally ruins an innocent student's life.
Based on Gerry Dee's real-life experiences as a high school teacher before he switched to comedy full-time, MR. D is a story about a charming, under-qualified teacher trying to fake his way through a teaching job, just like he often fakes his way through life. The premise shines the light on teaching from the teacher's point of view, and as it turns out, teachers don't know everything, especially Mr. D - who struggles to keep one step ahead of his students.