These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
When she leaves the show: is she ditching the egg with Horton, or does she genuinely believe she's made his life better by making him and "egg sitting circus sensation"? The song could go either way.
Big Lipped Alligator Moment: "Havin' a Hunch" comes out of NOWHERE, has basically nothing to do with the main story, has some weird dance involving glow-in-the-dark gloves, and is never referred to again. BLAM. The song does reunite Jojo with his parents, but almost no explanation is given as to how it did so.
Broken Base: Many Seuss fans either see this a loving homage to Seuss and his work, or an uninspired train-wreck made solely to cash in on his popularity.
Family-Unfriendly Aesop: Several, surprisingly, the most prominent being "If you get lost, go ahead and follow your hunch, and who knows, it might take you home!" Some others:
If you like someone a lot, it's ok to obsessively stalk them, even when it causes yourself bodily harm. If you manage to get them what they want, both of you will definitely end up happy.
If you imagine enough to make you space out randomly enough to flood your basement while taking a bath and get your parents worried enough to send you to the military academy, it's ok, you'll end up saving the world!
It's okay to give up your egg. Make no effort to change your own frivolous lifestyle for your child and dump it off with some guy who may or may not have agreed to care for it.
Unfortunate Implications: The meaner characters get R&B and Latin-inspired music, while the nice characters get vaudeville and folk-pop material. The Sour Kangaroo is based off of Aretha Franklin (R-E-S-P-E-C-K! Woo, please take that speck a-WAY!), and the monkeys... Well...
The military camp has lost its context about being about the Cold War, making it sound as though it's dismissing all wars as frivolous. That runs counter to Seuss's own views who, while he criticized the Cold War as "crazy", could be VERY pro-war depending in the circumstance.
Or one could take it as simply being against sending children to military school instead of looking into what the real problem is/sending them to military school to "make men" out of them.