Julius, covered in foam from the fire extinguisher, messes up his hair causing it stick up. We cut away, then back, and his hair is flat again.
When Julius goes to spray the workers with the fire extinguisher, he fires one that sprays smoke. In the next scene when he enters the office, he is covered in foam that obviously didn't come from the same extinguisher.
The drummer of the band Hail Caesar is obviously not really playing drums.