One of the funniest moments I can remember happened at my cousin's wedding reception in Nairobi a couple of years ago. I was sitting at a table with my younger sister and some old school friends.
The wedding had been very formal and quite long, with lots of speeches. Then the bride's uncle, a very serious and dignified man who's a retired judge, stood up to give the final speech. He'd clearly prepared it carefully and was reading from a sheet of paper. Halfway through, a gust of wind blew the paper out of his hand, across the garden, and straight into the fish pond. He paused, looked at the pond, looked at the guests, and said, completely seriously, 'Well, that was the best part.' Then he started dancing. Not just a little dance, but a full, energetic routine that he'd obviously been practising, while the band started playing behind him.
I laughed so much that I had tears running down my face and my stomach hurt. My sister was laughing so hard she couldn't breathe.
I think it was so funny because of the contrast. He was the last person anybody expected to do something silly, and the whole evening had been so formal that everyone was waiting for a chance to relax. His timing was perfect, too. Later, I found out that he'd planned the dance all along, but not the wind. I also think shared laughter is more powerful; when a whole room is laughing together, it becomes infectious. Whenever my family gets together now, someone mentions the 'judge's dance', and we all start laughing again.