Originally Posted by erikun
The problem is that Pinkie's antics are intentionally and very blatantly completely against even the magic of Equestria, it doesn't fit the setting unless that setting is a cartoon show on TV. Nopony wonders that Dash can fly or even perform a Sonic Rainboom, or sleep on clouds, or that Twilight can perform magic tricks, but they do wonder about Pinkie doing things that frankly only make sense if the whole thing is a cartoon, and the characters should not be aware that they are living in a cartoon!
It works because we're watching a cartoon, but the moment the characters actually acknowledge it as something real, within the setting, it doesn't work any more and instead conflicts with the setting.
Consider trying to treat the setting seriously and having Pinkie be able to do completely stupid things that should only happen in a silly cartoon and which apparently utterly defies the world view of all other characters. Suddenly you're not telling a story in a meaningful setting, but some weird, nonsensical bit of fiction in a silly cartoon setting.
Now, if you want to say that Pinkie descends from a long line of gypsies and thus has some sort of gypsy magic, that's fine if you can explain it and make it fit into the setting. But having Pinkie pie defy everything known about the setting and having the other ponies acknowledge this feat of reality defying is simply wrong.