Each 2-word phrase on the left side is a "disguised" and shortened form of a familiar saying. Here they are.
Rocky romance- The course of true love never did run smooth.
Terrestrial mollusk- The world is my oyster.
Chartreuse envy- Jealousy is the green-eyed monster.
Capricious fame- Some are born great, some achieve greatness, and some have greatness thrust upon them.
Attitudinal bias- There is nothing either good or bad, but thinking makes it so.
Craven scruples- Conscience does make cowards of us all.
Gluttonous guest- He hath eaten me out of house and home.
Invisible irrelevance- 'Tis neither here nor there.