I don't know what I'd do without water soluble pens - I use them for garment making and quilting, and I've often thought that they're one of many reasons why I'd be no good on Sewing Bee! My items
definitely need to be washed by the time I've finished!
I did once draw all over a present I was making for my Mum, only to realise that I hadn't picked up my soluble pen, but a normal felt tip...
... astonishingly I managed to wash it out. I'm still not sure how.