You can now put yourself on a U.S. dollar. The Federal Reserve Bank of Chicago went as far as to create a special app for iPhone or iPad to allow people to put their own face on a bill.
The Chicago Fed app is part of a wave of entertaining online tools developed by central banks globally to help educate people about complex central banking matters. In this particular case, the idea is to help people learn some interesting things about the security features on currency.
Quite a courageous move by the Chicago Fed. I could very well imagine a central bank being either outright legally prohibited or simply too conservative and unwilling to allow users manipulate banknotes in such way, even on an smartphone screen.