The Bush!
I spotted this on my way to a final the other day. Sadly, it was blacked out the next day, so the full humor of the alteration is a bit tough to see:
The blacked out part says “DIE BUSH!” It was spray painted on the sidewalk. Before it was painted over, the first word was crossed out in chalk and the rest of the text was added. The text is self-explanatory if you’ve taken German. If not, you need to learn a bit about German definite article usage. (The second Note on the page is the explanation you’re after.)