Jack is the hero of the play, yaknow. The plucky, smart protagonist who uses his wits to conquer his enemies and has an adorable duet with his love interest.
The whole opera is a study in what happens when a jerkass Mary Sue invades your plot and steals your leading lady, whereupon they literally ruin the lives of everyone around them.
This happens, of course, because Jack is not a tenor. Yup. Fate screws him over because his balls dropped too far as a jesterling.
Yellow suit, hnng. Now headcanon'd as a close cousin of Moist von Lipwig.