You can't say Paul wasn't fair. If he was going to make weird speculative drawings of other planets, then by God, he was going to weird speculative drawing about us! It says a lot about Paul's humility as well as his sense of humour that he could poke fun at just how far off the mark his speculations probably were.
This is how the Martians were supposed to see us. Apparently Earthmen are all chubby teddy bears living in pepper pots on the Louisiana Bayou. Most of their day is spent fondling enormous ears of sweet corn and stringing popcorn for no readily explained reason.