Squeaking with laughter at this thread; farted; laughed so much at myself I farted again.
Friends were getting married. It was only the second wedding I had been to and we were all young (b&g were maybe 23, I was a couple of years younger). Also important to the story is that I had been having non-epileptiform seizure-type episodes which were still under investigation.
It was a church wedding, but a different denomination from what I was used to, so I was startled by a very modern tune to some classic words. I can't remember off the top of my head but there was a bit where the women sing a bit and then the men repeat it. I found it completely absurd not least because I was surrounded by friends who were decidedly not singers but who were being supportively enthusiastic.
So I lost it, my shoulders shaking and tears streaming down my face. Dear friend sitting behind me assumes by the uncoordinated shaking that I'm having an actual fit, and grabs me in case I should fall. I am helpless to object or clarify, but other friends who can see my face have realised what is going on and are trying to calm me down and get friend to let me go and meanwhile the rest of the congregation is singing away heartily to this ridiculous to-me-to-you tune.
...
Actually my second most hilarious moment was also at a wedding. Our group of friends didn't think much of the bride, and the groom had had a series of minor catastrophes on his stag do resulting in a broken wrist. It was a smart civil wedding in a very swish hotel with beautiful grounds, everything very elegant and grownup. So when they announce the bride's favourite reading and it's "Wherever I am, there's always Pooh" by A A Milne ... well, Simon snorted and I just lost it. We were both desperately trying not to laugh because nobody else in the room thought it funny - including my DH and his DP. Every time either of us caught each other's eye, or the furious glares of our OHs, we went off again.
Sitting down for the breakfast, we're taking up all but two seats on a table, and we don't recognise the other two names on the plan. Until they introduce themselves as the groom's uncle and aunt, and calmly remark on how much we had obviously enjoyed the readings...