"Everybody, be a line note!" "Everybody, be a space note!"
While these are odd requests to hear a teacher bark at students out of context, there's a reason for them. If you ever walk past an elementary school music classroom and hear a music teacher demand that his or her class become line and/or space notes, these orders aren't intended only for students to learn the difference between the notes of the treble and bass clefs. Per a lecturer at a national high school music convention I attended in the '80s, it's a warning to the class that the teacher is at the end of his or her rope--especially if (s)he stands on a desk, table, or piano bench.
I suppose that's about the limit of anger that's advisable for a teacher to convey.
