A little outing but;
I once worked in a rather large company and they used to do quite a bit for charity, you could put your name down in the staff room and opt in to do runs, cycles etc. Being new and wanting to make friends I did..
I was asked if I would like to dress up as a bunny and stand with a bucket giving out freebies at a major London station, the girl I was partnered to do it with was a great laugh, you were taken out for lunch and dinner and it was a day out of work, not to mention I did my bit for a well loved cancer charity.
I came into work and the girl at the desk gave me the costume in a work branded bag and said “put this on and your coat over the top, leave off the ears and the head of marketing will take you and the other girl to the station in a black cab in about 30 mins!”
So I head down to the changing room, get changed, faf about really look at the time, it’s been 31 mins, panic that the others might be waiting for me/ go without me and run back upstairs dressed as a bunny with a coat over the top.
Upon returning upstairs there is a different girl on reception, foolishly I blurted out “have they gone?”, she responds “they’re just leaving now in the coach..”
I head out the front and see this couch doors shut and knock on the window and the coach driver lets me in, I think to myself it’s odd we’re now going on a coach, maybe there are more than three of us? Maybe there’s a training course going on some are attending and they’ve tried to save on costs.
Everyone on the coach looks a bit solemn and I see my manager and ask where the head of marketing is, she scowls at me and says “I don’t know sit down”
So I perch next to her telling her how excited I am for this, bit nervous to, it was out of my comfort zone and I’ve not done it before, I believe I also used the line ‘someone has too..’
She looks at me in disgust and says “I’m sorry?” I respond by asking her why she’s here? “I thought there was only like three of us, can’t believe there’s this many going..” She looks visibly angry and hisses to me “because i bloody thought a lot of Dave!”
It suddenly clicks.. 
About a month a go a well respected colleague had died unexpectedly of a brain haemorrhage after working for the company for thirty years, the business had put on a coach to his funeral.
I looked round the coach and my suspicions were confirmed a coach load full of mourning employees wearing black.
I start to really panic and tell my manager “I’m not meant to be here, I’m dressed as a rabbit”
She angrily tells me to be quiet and I end up attending the funeral of someone I don’t really know dressed as a rabbit.
Absolutely mortifying..
Never lived it down, never should.