Long back in one of my older companies, I had setup a reminder in my Outlook to pop out ever hour saying "Drink Water". It might sound funny but its true. I literally had to remind myself to drink water or there would be days when I would have had just about 2 glasses in the entire day. So this seemed to be best possible way to remind myself to drink water :)
Few of my close colleagues used to really make fun of me because of this reminder. And once when I went away from my PC they (Manish Sinha & Anshul Sharma) changed the message but obviously unknown to me. Those days we used to use Windows 98 which didn't have a password system lock option.
So when I came back and was really engrossed in something and suddenly the reminder pops up saying "Drink Beer!" Since my mind was totally lost into the work I had to read it 5 times to understand what it was saying and that I was not hallucinating and also to realise what had conspired behind my back. And I didn't have to think hard at all to figure out who must have done it. So when I looked at them, they were giggling sitting at their workstations!
That time I didn't find it funny at all but later I had such a good laugh thinking of the incident. :)