Déjà Moo

Listen up, chucklehead! You're so dense, light bends around you. "Déjà Moo" is a play on "déjà vu." "Déjà vu" is that weird feeling you've experienced something before. The joke replaces "vu" (seen) with "Moo", which is the sound a bull makes. The joke implies that you've heard the bull (or its story) before.