Well he IS made of mighty Oak. I guess if you are doing a wood robot, you choose the best wood there is. And you gotta like the irony of things. Wood hitting you for littering, how about that.
I'm guessing the thing on the tree in panel one might be a Caterpie, and the red and tan mushroom might be a Ramblin' Evil Mushroom from Earthbound. I highly doubt this next one, but is the red-green plant a variant of a Deku Baba?
There's at least one more easter egg. I will give you a freebie and say you had a good idea in saying an Earthbound enemy.