Apparently, Tiana does wish upon a star, as her father always gave that advice, but he also said that you have to work hard, too.

It says that in a newly-released feature on the Disney home page.
And in regards to the so-called "farting", they showed that whole scene where Ray meets Tiana and Naveen on the Disney Channel and in that un-altered scene, it's only a tiny squeak. So, it's obviously been altered to appeal to...I don't know what demographic to be honest.
And the butt expanding bit makes more sense in context, but it's also not a fart joke from those who read the leaked Princess and the Frog storybook.
And I don't see why people are making such a fuss about farts in a Disney film as if it's in response to Shrek. Does nobody remember Pumbaa in The Lion King? A fair amount of his jokes center around his flatulence problem (heck, there's a whole section of the "Hakuna Matata" song devoted to it) and Timon and Pumbaa are often cited as the best Disney sidekicks.