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That rebus is clever, but it doesn't entirely work for me. What he says is a "bush" looks more like a tree, and a Christmas tree at that. It does break the fourth wall in quite a big way, as well. I mean, pointing to the artist's signature? I didn't know a comic strip character was allowed to do that. Unless, of course, she's not pointing to his signature, but instead has written "Ernie Bushmiller" on the ground for us.
I'm probably thinking a little too hard about this.