Everyone (including That Other Wiki) keeps saying that the lyrics of "Turtle Power" were changed for this so Raphael is now the "bad boy", instead of the leader. Yeah, I checked. They're not. The lyrics are exactly the same. What gives?
"Everyone" in this case includes Partners in Kryme, who specifically state on their Facebook that they changed the lyrics for the game remix.
The Turtles are presented the chance to become human or save the world, and upon their agreement, Raph... smashes the bottle of purple ooze. This ranks quite highly as one of the most stupid acts EVER. Of course they needed to save the world... who's to say they can't save turning human for LATER?! Or even put the stuff in the fridge so that in the future when they're 20 or so they still have the choice? Or use it to turn Bebop and Rocksteady into weak humans again? There's absolutely zero justification for this. What the hell was going on in the writer's head when he didn't think we'd notice how stupid that was?
It's worse than what you're saying. Donnie makes it clear that one sip would make them humans on the outside, but still the same inside. So, they could turn into humans and save the world. I guess the idea is to send a "be yourself" message, but it's really poorly managed.
That would only be temporary though. If one drop only lasted a few seconds then wouldn't one sip only last a few minutes? Furthermore, considering how their shells more than likely give them a boost in defense, isn't it for the better that they didn't drink any mutagen?
Wasn't stopping them from saving the mutagen for later.
I think it boils down to Honor Before Reason. The mutagen was driving a wedge between them and they decided they didn't need it, and rather than using it to defeat Bebop and Rocksteady (which could have been turned on them in a critical moment anyway), they destroyed it. I took the "still the same inside" to mean that they would be physically human but have memories of being turtles and ninjas. They would likely be substantially more fail and vulnerable in mere human bodies, and would probably have to spend a while remastering ninjitsu in new bodies.
April tells Stockman that she's got a boyfriend, and he asks her if her boyfriend knows the difference between Pi to the third decimal point and Pi to the fifteenth. Does... does that question actually make sense? I mean, isn't the obvious answer that there are twelve more digits in Pi to the fifteenth decimal point than there is in Pi to the third?
It's an awkward callback to the scene where April is explaining the difference between nerds and geeks (as the Simpsons put it, "nerds are smart"). He's trying to convince April to date him instead of her "boyfriend", but he's rather socially inept and infatuated with her. It's no surprise that he asks kind of a dumb question instead of something more deep or insightful.