When I was wee my best friend had a color change Hello Kitty and I was as jealous as a 7-year old could be. What I wouldn't give for one now.
I think this is more of a case of pre-stalgia as technically these don't even exist yet.
Available at: Thinkgeek http://www.thinkgeek.com/homeoffice/supplies/e5da/ ($10) Via: Cubicle Bot http://cubiclebot.com/office-supplies/floppy-disk-sticky-notes/
If you didn't have at least one of these toys as a kid, your childhood didn't count. Don't worry, here's your chance to make it up to yourself. And yes, they totally work.