I gave up my planning period to teach an extra class because nobody else would teach them and got an additional 25% of my salary. I knew the extra $$ was temporary - so I wanted to do something special with it instead of just adding it to my monthly income.
I teach in an inner-city school and the year-of-my-extra-class was total chaos - we did not have a principal, had a shooting at school, had a gang attack, etc. My extra class was the last period of the day, all kids (well, technically all adult males) that had failed 9th grade English 2, 3 - even four times. Almost every kid in there was out for weeks at a time because they'd get put in jail - then they'd come back. I have about a million stories I could tell about that class - it was the most intense, challenging thing I have ever done in my life - but they honestly made me laugh every single day.
Now, whenever we are at Disney, I always say out loud "thank you fourth period - and God bless you - whatever jail you might be in."