Happy April Fools
Looks like you got fooled.
I know the community has decided to make the fake new messages bar or the fake signatures a policy violation but as an April Fools joke, it couldn't harm anyone. Don't worry the about the banner or incorrect signatures as they automatically shut off and revert back to normal after April Fools Day is over.
How many people got fooled in... edit
2012: edit
People were fooled 46 times.
2013: edit
People were fooled 68 times.