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Jack is a compulsive liar. He lied about burning the mural, and Marge believed him. When he later burns Skinner's car, she realizes that he was lying. He later admits to burning the mural, but not the car, even though Marge saw him burn the car.
Marge later learns that he was imprisoned at least one other time for an incident involving a young couple and a tractor. He participated in the prison rodeo where Homer injured his back.
Although he is a convict, Crowley is a skilled painter first noticed by Marge for his painting of Jimi Hendrix (which was painted with pudding). Crowley was later employed to paint a mural for the Springfield Elementary School. Principal Skinner had Crowley change his mural from an edgier style to a more childish and colorful image that everyone hates during the reveal. Enraged, Crowley burns the mural, and later, Skinner's car. He is last seen going back to jail.
He also revealed that he was Jewish.
 Relationship with other characters
Crowley is seen by Marge to be a gifted artist and a troubled, but nice person. Marge trusts him unconditionally at first, but later sees that he is bad person when he burns the mural and car.
Skinner and Crowley's relationship is rocky from the start. Skinner talks down to Crowley, calling him "college boy." Skinner sends Crowley over the edge after criticizing Crowley for the mural that Skinner drew on the napkin.