"A drill instructor" joke

A drill instructor at Airborne school was lecturing a group
of new troops on making a proper jump. He told them:
"When I yell Stand Up, you Stand Up. When I yell hook up,
you hook up. When you go out the door, yell' Geronimo!' and
wait for your shoot to open. Got It? Good, get in the plane."
After a short flight he yelled "Stand UP! Hook UP!" and began
shoving the troops out the door. Just after the last trooper
exited, the sergeant shut the door. Suddenly, he heard someone
knocking on the door. He opened it to see a private flapping
his arms trying to imitate a seagull. The private looked him
in the eye and asked What did you say that SOB's name was?