A few spring to mind. A brother got up to give a talk and when he adjusted the lectern height to put his books in the right position he didn't tighten it properly. As he began his talk he gripped it with both hands and it suddenly dropped to which he exclaimed "oops I've got a wobbly rectum".
A visiting speaker was giving a talk where the outline touched on horoscopes, he then pulled out the newspaper and read out every horoscope. There were complaints to his body of elders!
A local elder who wasn't the sharpest tool in the box gave the talk "a godly view of sex and marriage". It seemed that he wasn't entirely clear on the specifics of how procreation worked and got himself in a muddle. When describing the point where an embryo becomes a foetus be inexplicably termed it as when the "embryo becomes a fully full fully". News of the talk spread to those who weren't there on the day and those in neighbouring congregations and a number of copies were passed around for amusement value.
And of course in every congregation someone said orgasm instead of organism.
