WONDERFUL film. One of my favorites! But it always kind of puzzled me; it looks as if Betty and Bill (the mom and the man who owns the diner) were already attracted to each other before the drastic changes in Pleasantville started to occur. So do you suppose there was a bit of a thing between them on the show itself, and David & Jennifer's actions just ignited the flames of passion between them that was already there, or did it happen BECAUSE of their actions changing Pleasantville? That's one of the few things in the town that seemed out of place to their existence before things changed.
Bill was a very peripheral character in the tv show "Pleasantville," hence he wasn't really fleshed out. He couldn't handle simple changes to his routine and got flustered when he had to make decisions or do things differently. Hence, I don't think anyone ever gave much thought to Bill as a character, what he may want or need. But I think you are right: without it being written into the scripts, Bill was enamored of Betty, but couldn't do anything about it. Perhaps without it being obvious to anyone, he was kind to Betty, paid a bit of extra attention to her, listened to her. That kind of attention would be very attractive to a woman whose whole life was taking care of others, her children and husband. No one had ever put her needs first.
So, yeah, I think there was already some attraction there, but the writers of the '50's tv show would never recognize it and certainly wouldn't write anything to encourage it. It wasn't until the show/city started changing with the new Bud that it was allowed to blossom. But we, as viewers, could and did see it; it wasn't such an outrageous idea to us that a married woman could be attracted to another man.
I always interpreted it as Betty and Bill never meaning to see each other. "Betty certainly knows about Bill because her son works at the Soda Shop and Bill knows about Betty because she is his employee's mother, but as far as the way Pleasantville has both characters written into the show, they probably were never meant to interact with each other. I think that because Bill had to come to the Parker house to check on Bud since David sort of "messed" with the flow of how things go, he and Betty suddenly saw each other for the first time and instantly fell in love. They were written to know about each other, but never to see each other, or at least that's my interpretation.
But when Bill came to the house, it was clear that they knew each other and there was attraction there. Bill got flustered, and Betty got....well as close to giddy as a married woman would be allowed to get about a man that wasn't her husband in the '50's. It wasn't just the mom of an employee and a shop owner. There had obviously been other interactions--watch David's reaction. He can tell something is going on and it makes him anxious; he hurries Bill away from Betty.
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No, David. No one is happy in a poodle skirt and a sweater set.