For example: we had a 'faithfull' brother getting older and confused. When something did not really went as he liked it (didn't get the answer etc) he shouted very loudly 'God doom me in the hell!'
One time I had to do the closing prayer on the midweek meeting. I was just back from holyday, and had an encounter with two chinese sisters the last day of my holyday. When praying I got confused when thinking 'I must not say: O, thank you Jehovah for those two chinese sisters that were in my bed last night'. While confused I did manage to finish the prayer normally without saying that thought aloud.
Later the PO came to me and said: what kind of prayer was that? I did not understand anything, did you speak Chinese?
any other bloopers?