I heard a first officer one day, telling ATC they needed to run the engine up to 70% for a crossbleed start. Caused a major flap. Safety cars running around everywhere and ATC insisted the plane be towed away to another part of the field for the start.
The Captain had obviously not heard what the FO had said on the radio, and couldn't understand what all the fuss was about.
It was after all, a common event. I was nearly going to tell the poor chap what his offsider had said when they managed to work it out.
Lesson for the day...choose your words carefully. I hope the FO bought the first round.