I'm all the time eating Oreos (Don't judge ;) ), so this is an easy one to play on friends!
Just use a butter knife (or whatever works) and scrape the Oreo cream off the Oreos and replace it with a thin later of white toothpaste.
Put your Oreos back together and place it in the freezer for toothpaste to harden. You will LOVE the expression on your friends faces when they try this. Just be careful that no one actually swallows, of course.
What are your favorite April Fool's Day pranks? Are you usually the Prankster or the one getting tricks played on you?
Have a fantastic day!!! :))