Graffiti by omission

I wish I knew if there is a proper term for this... it's something I noticed a lot when I first moved to Sydney, especially on trains: people deface signs by scratching out or subtly changing letters to make them humorous.

E.g. on trains: "at night time, rave with the guards under the blue light" (where "rave" used to be "travel")

The other month I saw a cracker on the side of a van - I keep seeking it parked near my home, and I'm surprised it hasn't been fixed...

Originally, it would have been:

"Decrease your home loan costs. The broker with nothing to hide!"

Now, it reads:

"Decrease your melon costs. Broke with nothing to hide!"

Made me chuckle!
Have you seen any graffiti by omission lately?