One from BA - onboard a 737 intended to fly Koln-LHR
Koln gets very intense storms during the summer - I was sitting in 1A as we taxied out to the runway watching the bow wave from the nose gear as the rain pelted down.
We lined up on the runway and the engines began to spool up, then rapidly spun down again closely followed by a clearly audible "What the
do you think you are doing?" through the cockpit door.
The aircraft was then taxied off the runway to a holding point where the skipper proceeded to tear strips off his co-pilot for about 15 minutes until the weather had passed.
I'm guessing that the episode was only heard by the first few rows of passengers, but it had us chuckling.