The two protagonists are Trapped in TV Land and teach the citizens of TV Land to be more real, implying that everyone in the eponymous town was a real person who just needed to be "fleshed out", so to speak. But to do so, they take the place of Bud and Mary Sue, the children from the TV Show. Mary Sue is literally Put on a Bus to a college that showed up when the world became, well, realized. But this doesn't solve the problem with Bud, since David went back to the real world... and even worse, it creates a new Fridge Horror: Jennifer/Mary Sue never returned to the real world. Surely someone would have noticed at some point?
I just assumed that the real Bud and Mary Sue were in the real world, and learnt the same lessons from the other end.
Fridge Horror: The TV repairman doesn't seem surprised at all that David and Jennifer ended up in Pleasantville, does he? And he never acts to try and get them out either, despite offering to consider it once or twice if they asked nicely. Toward the end, the repairman wants Bud to leave so he can "make everybody happy again". How many other kids have ended up in Pleasantville and been the subject or cause of incomplete revolutions? Where are they now? Did the town do a hard reset each time?
The Repairman makes a big deal about how long he'd been looking for someone who really deserved Pleasantville, and how many times he thought he'd found someone, but was disappointed. It sounds like he never found anyone "worthy" of the magic remote until he found David.
David and Jennifer are the first. The repairman gave the remote to David because he was able to answer the questions about the more obscure episodes.
The changes are all kicked off by Jennifer, who wasn't supposed to be there in the first place. David seemed perfectly happy to live in his escapist fantasy and not make any waves. What if Jennifer hadn't been drawn into Pleasantville with him? Would David have just lived the rest of his life in this unchanging, lifeless, black and white world?