Luke's face is an expression basing on the change in Luke Skywalkers face from A New Hope to Revenge of the Sith. As everybody knows the actor, Mark Hamill, got hit by a car in between the shooting of the movies.
Luke's face can be used as:
1. an insult
2. to win an argument/"your argument is invalid"
A: Shouldn't it be called "the Early Early show" since it's on past midnight?
B: Luke's face!