Question: Generate a question that has the following answer: Mr. John Gribble for the following movie plot: In high school, Marc Pease (Jason Schwartzman) ran out on his performance as the Tin Man in a production of The Wiz, succumbing to his stage fright despite his mentor Mr. Jon Gribble's (Ben Stiller) encouragement. Eight years later, he is dating Meg Brickman (Anna Kendrick), a high school senior who is bitter about being in the chorus and not having a principal role in Gribble's latest production of The Wiz. Marc is keen for Gribble to produce the demo tape for his a cappella singing group Meridian 8 (which has already lost four of eight original members). Gribble, however, tries to avoid Marc, frustrated that Marc refuses to leave him alone because of the friendly advice he gave Marc eight years ago. While tidying Meg's bedroom, Marc finds a tape labelled "Meg singing", but discovers after he listens to it that she is singing with Gribble, and at the end of the song, their noises suggest that they are having sex. Meg, meanwhile, begins to doubt Gribble's sincerity when he tells her what a terrific singer she is when she realizes that she is always in the chorus. Questioning whether she even enjoys singing, she decides to quit. Marc drives to a performance with Meridian 8, where the only way he can keep the group from splitting up is to lie that Gribble has given them the chance to record in a studio. After insisting that he should sing his Tin Man's song, he starts crying on stage, and is later forced to admit that Gribble has not yet responded to his request to produce the demo. That night, the opening night of The Wiz, Marc is working as a chauffeur for a high school prom couple. After dropping them off and cutting off his frequently ridiculed ponytail, he arrives at the show in the interval. He unsuccessfully tries to discuss Meridian 8's demo with Gribble, who brushes him off, then learns from another bandmate that they are losing another member. After hearing the Tin Man's song from outside the auditorium, Marc goes inside and drags Gribble out into an empty classroom. Marc confronts him about his empty...
Answer:
Who is the former teacher/mentor?