Why did the Maya Rudolph cross the road?

This is one of the most infamous clips in the entire movie.  I find it extremely funny.  I think I'm able to do this because the movie never actually confronts us with the poop itself, just a little throw up.  What we are treated to is the characters pain and struggle as they sweat it out in the bathroom. They try to keep it together as best they can but they all fall apart. All the while the real mess is safely concealed under lots of fabric.
One of the best parts of this scene, though, is the contrast between the two settings of this scene. There is the refined dress shop, filled with dangerously white carpet. The bathroom itself is just as refined, but the scene inside of it quickly devolves.  The movie cuts between the two of them making the humor in either even funnier. The bathroom is full of women screaming at each other as they destroy it. It's loud and chaotic. Outside, in the store, Annie is doing her best to maintain composure and Helen, who didn't eat the meat, is completely fine. We laugh as Helen torments the sweaty Annie by talking about her distress and even getting her to eat.  The two of them are basically whispering with refined piano music playing in the background.  It's quiet and sophisticated.  Going from the quiet of the store makes the turmoil of the bathroom more jarring.  Then going from that back to Annie's quiet suffering makes it more fun to watch the pain in her eye.
I don't believe trying to relate Mr. Hankey to the Bridesmaids scene would really work.  Their humor is different, they're mainly just tied together by the presence of poop.  Mr. Hankey is about this crazy character and what he represents.  South Park makes him a Santa like character. On the other hand, Bridesmaids focuses more on the behavior of the characters as they perform this normal act, taken to an extreme by the questionable Brazilian food. Poop humor is a thing, but not all humor involving poop is necessarily poop humor.