redon on Pirate King forums:
the Popeye comparisons is a good one, because one of the things that "awakening" gives Luffy's fruit is "freedom". And that "freedom" allows Luffy to fight as he wants, and in this case (for now) it's to fight as if he were a cartoon, with all sorts of crazy things.
And as you can see, that doesn't only affect him, it also affects the enemy (that's why Kaidou in one image also looks like someone out of Looney Tunes or something).