Replying to Prank Idea

Ok, so theres a dude up my street, and it was his fiftieth birthday yesterday, and theres a marquee type sign where you put the letters in the empty spaces in his front yard that says:

"         Looking Good!          "
             Isn't It Nifty
           Bill Is Turning
                    50!

He's usually pretty chill and I'm thinking about going up there tonight and changing the sign around for jokes. (NOTE: There are two sides of the sign, so I have two of each letter to deal with.)
What should i change it to?
Is it worth it?

Help Me NS!