Every twist, every alteration, every mockery, every shredded remains of The Fourth Wall, every subversion of cartoon film-making that this short deploys. The humor in this short is Meta before people even understood what Meta was.
"This is a close-up? (beat) A CLOSE-UP, YA JERK! A CLOSE-UP!" Camera zooms WAY up to his veiny eyes.
"Now how about some color, stupid?!"
"NOT ME, YOU SLOP ARTIST!!!"
Daffy's expression the first time he tries to speak when the sound is being messed with (when he opens his mouth but we hear a rooster crow).
And then Daffy getting angry with his eyes turning red before he screams and jumps around, before yelling, "AND I'VE NEVER BEEN SO HUMILIATED IN ALL MY LIFE!"
And when the animator turns out to be Bugs Bunny. This revelation is the absolute cherry on the cake.