Just think about it, you and a couple of friends are watching classic South Park or something edgy. And then, some person comes who's not even a fan of it, demands changes (censorship) or outright turns off the program. Just why do people do this? Why do they ruin everyone's fun?
Seriously, they are. This is by far the most important issue, if they made their asses fatter it would improve viewership. If they made the ponies thicc prudes would complain, which would only draw in even more viewers. Twilight Sparkle, the protagonist of the series has a fat ass, and her teacher Princess Celestia, who's ass is even fatter.
The main reason is uncanny valley. When something looks human but not quite. A perfect example would be a robot trying to mimic being human, it looks unsettling. It's somewhat insulting towards the ponies, you have Twilight Sparkle there a beautiful unicorn and you can't embrace her just because she's not fully in human shape, even though she has all the qualifications to be a sapient-minded
Was that actually an episode?
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Fluttershy seems to grow larger in many episodes. She can also shrink back down again.
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Now this, I must see
... where can I see this, exactly?
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Look up giant in derpibooru. It is how I found out. Make sure spoiler tag isn't locked.
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https://derpibooru.org/images/2397056
https://derpibooru.org/images/2398171
https://derpibooru.org/images/2380325
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Huh.
...
kinda weird.
...
Still not as strange as some things I've seen.
It's still an annoying running gag though. Heck all of Pony Life's running gags are annoying. -_-