How many times can you use amnesia in a show with seven seasons? How many times can you reveal that Character A is secretly related to Character B? How many times can someone get killed but then miraculously get better? How many times can you introduce absolutely world-breaking plot devices, only to forget about them immediately?
The answer for all of the above, for Once Upon a Time, is THERE'S NO FUCKING UPPER LIMIT.
It did have this absolutely fantastic exchange though...
Grumpy: We're all going to go hang out with Happy.
Snow White: Didn't he get turned into a tree?
Grumpy: Yeah, but we fixed that months ago! We do things when you're not around!
'Fables' was a comic book that was the first to use the idea of characters from fairy tales living in the modern era. When people realized that everything was already public domaine we got two shows, neither as good as the comic.
It was created by some of the same people who made Lost. Both shows relied heavily on flashbacks to make the shows seem more planned out. Both relied on inconsistent mythologies to fake worldbuilding.