Seems that last week Mike Mularkey was calling plays from the press box. He relayed them to Trent Green, who then called them in. While that part we know to be true, I can't confirm the rumor that there was a 5th grader who then called them into John Beck.
I assume it went something like this:
Mike says "Quick out to Marty Booker on 3"
Trent Green says "Outside run to Lorenzo Booker in the tree"
The 5th grader says "long pass from the spilt tee"
Beck tells the team "Let the rush sack me"