Like with the Antagonist section, it's hard to find a pair of foils in Cannery Row because nobody acts like much of a jerk. We wanted to put Dora and Mack together as foils, since Dora is a good businesswoman and Mack couldn't hold onto a dollar if it were glued to his hand. But then we realized that, at bottom, they're both fundamentally good and generous.
Doc and Henri, however, are a potential set of foils. Not because Henri is a big meanie where Doc is good and kind, but rather because Doc's happy to have forty people hanging around his bedroom, while Henri lives in a place that's really only big enough for him. (See how authors can use location to tell us about character?) That means that Doc is wide open and social; Henri's an introverted loner.
On the other hand, neither one of them has a girlfriend that sticks around very long.