Maybe a stupid question, but how did it come about that Truman Burbank got a catchphrase?
The answer is "don't worry about it, the movie needs it in order to work".
But if we're considering Truman's upbringing, and the sitcom-esque nature of the concept, it's not like the writers came up with it one day and then repeated it due to fan reaction. Someone either had to feed it to Truman and hoped it would stick, or create an environment around Truman to pump him up when he said stuff like that.
But then I start wondering, wait, did Truman grow up on sitcoms? Was he allowed to see shows as long as they don't reference the real world, and if so, wouldn't he think catchphrases were campy and weird? Did they not allow him to have narrarive tv at all, so the idea of a writerly trope never seeded in his brain?
I'm beginning to think this whole Truman show idea might not have been a healthy for someones mental development! /s