This is a great prank to pull on people because even on april 1st they won't see this one coming.
The setup is quite easy. While your colleague is away just put this melting popsicle paperweight on his papers and wait for him to get back. As soon as he sees the melting popsicle he will be running back to his desk . Various effects may happen then. Freaking out and getting the popsicle off and then noticing it's fake or complaining for a good 10 minutes about not leaving coffee and snacks on other people's desks. (that last one was pretty fun, we really had to convince him it was fake so he would shut up :p)
And after you pulled the prank it makes a pretty neat gadget for personal use. I use it all the time as a paperweight in my room. And this way you can fool visitors as they come into your room and notice there is a popsicle melting on your papers!
Disclaimer: This is a pretty innocent joke but always be carefull with whom you pull this prank. Don't forget that people who are under a lot of stress can make the final snap into total rage after a prank like this. I'm not responsible for anything that happends with you, other people or the popsicle.
Note: this 'ible is explained at child level without including the "get your parents to help" stuff. I teach children ages 6-12 so it's not easy to explain something without doing it at their level :)
About spelling mistakes and wrong sentences: I'm truly sorry for this but alot of words that I use in this 'ible are not in my daily vocabulary. Also English isn't my first language so keep that in considiration. If you spot any mistakes please comment and I will change them :)