The TMNT Entity blog reviewed recently a series of early 90's UK Ninja Turtle comics, and the OP went into some observations about a key aspect of the 1987 Turtles' in-universe origin:
So in the Fred Wolf/Archie/Playmates origin, the grate the Turtles fell through led to where Hamato Yoshi was living at the time. The Shredder, in an attempt to kill Yoshi, poured mutagen through that same grate, covering the baby turtles.
Bebop and Rocksteady essentially try to copy Shredder's original failed scheme, but not knowing where the secret sewer lair is (discounting all those times in the Fleetway comic where they do know), they attempt to dump the mutagen down the one place where they know it had hit the Turtles in the past: That particular sewer grate.
None of this really makes sense if you spend an extra second on it, as Shredder dumping mutagen in the sewer to kill Hamato Yoshi was always one of those weird parts of the Fred Wolf origin that barely held together (How did he know Yoshi was down there? Why didn't he just attack him in person? Why did he pour mutagen of all things on him instead of, I dunno, napalm?). Still, it's the only reason I can think for the writer to have put that bit of happenstance in the script.
http://tmntentity.blogspot.com/2016/07/tmht-poster-mag-4.html Here's my initial response, via blog comment:
I personally go and back on that particular subject a lot, but I'm ultimately willing to get past those serious logic issues as I don't mind the "it sets up the Shredder as actively responsible for the Turtles' creation vs. most other media where he's more of an indirect influence" premise. Also, given how most of the Yoshi/Saki backstory had to be censored, downplayed or glossed over for 80's animation censors, David Wise probably did the best he could think of, at the time, and called it a day. While I'm at it about the Fred Wolf Yoshi/Saki backstory, I often think about how the series could have handled Tang Shen, but that's for future commentaries.
Lastly, "why mutagen instead of napalm," my current headcanon about that goes, "he could have originally thought the mutagen was poison, since it was said to be experimental with Krang outright confirming he intended to use the mutagen to 'destroy Yoshi,' and maybe didn't know what it could really do at the time." Probably thought it would have been a good slow agonizing kill. I tend to support my theory with his later use of the Doku plant against April in "Enter: The Fly." Only this time, it really was poison.
Okay, back to the MST3K mantra, "it's only a TV show..."
As for the actual issue, it seems more of "like the concept, not the execution" as Bebop and Rocksteady showing "initiative" could have been potential comedic gold. Instead, what we got a near-rehash of Baby-san's rampage from the first Usagi episode (or it felt that way to me in reading the synopsis). Nevertheless, I appreciate its effort of intentionally replicate the Turtles' origin, or what Mark called "laborious poetic symmetry." When comparing to the other three Poster Mag stories, it's actually a little more ambitious. Vs. fighting in gliders, a costume party fight, a foiled bank heist, etc.
I posted the comment late, so forgive my clean-up re-editing.
Lastly, I'm copying/pasting my second comment, since it's an needed addendum to the first:
In hindsight, I probably should have added a line on Usagi's second episode, as it actually did show Bebop and Rocksteady using initiative to hilarious results, via their fuel-stealing. Whoops. Forgot about that, but I now feel better about the Baby-san parallel. The Doku plant analogy was something I've thought about for years, so glad I could finally show it off, here.
Might be wrong about this, as I wasn't sure enough to add it originally, but the mutagen/poison logic also could have been a by-product of Fred Wolf Season 1 Shredder's characterization. In that, he was a tad more deliberate in his evil vs. the Leeroy Jenkins behavior he'd later have. Back then, could have been more patient with Yoshi dying a slow death vs. later. Not to say the Leeroy Jenkins behavior wasn't there from the start, either, as Mikey goaded him like a master at the end of "A Thing About Rats."
I'm posting my commentary mainly for future reference, as I have been asked about the 'mutagen used to destroy Yoshi' logic issue by friends and/or fellow TMNT 87 fans. And now you know the rest of the backstory, as to borrow from a famous Freakazoid quote.