Well I actually did that one myself. I do not know where I got the idea, it was from random internet surfing, and I wound up on a forum with a ton of these. I didn't go joining the forum just to post my own because it had been locked for a year at the time I saw it.
There may be some sites dedicated to doing this, but I wouldn't know about them.
It's still a pretty popular thing to do to Garfield comics though. One of the funny things was that the poster of the thread made a joke hypothesis saying that Garfield comics are so bad that
removing content is the easiest way to make them of acceptable quality.
Alas, my favorite Garfield strip(s) would have to be the series that starts with this:
http://www.garfield.com/comics/vault.html?yr=1989&addr=891023