I dated a co-worker and we would act very professionally in front of others... until the elevator doors closed where she would jump me for the 10 to 30 seconds we had in there.
One day the doors close, she jumps and wraps her arms around my neck, and we hear the sound of the doors start to open again because someone pushed the elevator call button before it properly left. I THREW her aside out of panic and she went flying into the opposite wall and recovered like she tripped just in time for the doors to open. We kept our shit together just long enough for the person to get off on the next floor and we both broke down laughing.
It became the thing she would joke about the most when she was trying to embarrass me a little; the time I launched her across an elevator.