Someone had done this in my town in 07 to about 42 stop signs which cost about 46,000 $ for the city to replace. The writing looks almost exact. I didn't feel it to be an effective slogan at the cost of community funds.
All around Seattle we have signs that say "Stop for me it's the LAW" with a person in the standard walking pose. What someone decided to do was spray paint a C in front of law and draw a hilarious little claw on the walking person. Every time I see one I smile. Street sign fun shouldn't be illegal if you can still read the sign; it brings humor and life to a cookie cutter object. Here is one: [link]