VERTIGALA

I know there have been a lot of popular theories up to this point that Augustus would be Jonah Magnus, and episode 4 puts a lot more evidence out there that would seem to support this idea.

Here's what I thought was relevant to this theory after listening through the episode twice this morning:

Augustus is voiced by an older man who I don't think we've ever heard before, and we've never heard Jonah's actual voice either, since he's using Elias's voice throughout all of TMA as far as I'm aware. He sounded vaguely like Jurgen Leitner to me, although I think this is just on account of the fact that the VAs sound similar and not indicative of them being the same person or being meant to voice the same character (I didn't catch who voiced him in the credits and I couldn't find it online, if you all know please tell me and I'll update this)*

The incident report is a very old document, with a writing style and tone reminiscent of the old statements/letters to Jonah in the early days of the institute. It seems like it'd be right up Jonah's alley.

The episode revolves around a man succumbing to a dark power and eventually dedicating himself to it (the freaky bloodlust violin vs the Eye) and recruiting a younger man, in this case his relative, to serve this violent power (though probably after his death in this case, unlike with Jonah), which has some parallels to Jonah's recruitment of Jon and the rest of the staff in TMA.

We don't know much about the universe of TMAGP yet, but we know there is a Magnus institute that has aldready been linked to Eye-esque characteristics like paranoia, suspicion, (fatal) curiosity, and eyes as of Ep 1. It is possible that Augustus could be a version of Jonah from the TMAGP universe, rather than the same Jonah we dealt with in TMA.

.JMJ error could stand for some combination of Jon, Martin, and Jonah's initials, given that Chester and Norris also have Jon and Martin's voices.

In the TMA finale, Jon, Martin, and Jonah (though I assumed he was dead at that time) were close to where the fears were sucked out of the world and sent somewhere else, and Jon and Martin may also have ended up in the OIAR's computers in some form.

On the other hand, here's some evidence against Jonah being Augustus:

The other Jonah theory I've seen posits that Jonah took over RedCanary's body when they went down to investigate the ruins of the magnus institute, assuming that "canaries should stay above ground" and the gory photo of eyes was meant to represent RedCanary's eyes having been ripped out and presumably replaced with Jonah's. If you interpret things this way, it makes it less likely that Jonah is in the computers, unless you think both TMA Jonah and a hypothetical TMAGP Jonah are both around at the same time, though this theory is also a little shaky itself since it seems to be based on only a couple pieces of evidence so far. I first saw a post about this from @thermodynamic-comedian though that post says she saw other people discussing it, so please lmk if you know any major contributors to this theory and I will add them in here too.**

The fact that, to take over as the Eye's pupil, it was implied that Jon had to actually kill Jonah, and he was seemingly dead as of the TMA finale. Death was usually a very hard line in TMA except for a few avatars of the End and near-deaths where characters lost some of their agency (and/or humanity depending on your interpretation) to become an avatar instead (which Jonah already was), so him being back after seemingly already having been killed off isn't super plausible unless it's revealed that he didn't actually die in the first place.

It seems like there's enough evidence at this point that this theory definitely feels viable, though there is nothing definitive that I'm aware of, and there are some things that point to other explanations.

I personally (this is now entering pure opinion territory, tread lightly) don't love the idea of Augustus being Jonah, because I'd prefer it to be someone or something new to the series or something otherwise more surprising, rather than the same central antagonist as last time. There certainly are ways they could pull this off well, and bringing him back definitely doesn't tarnish the story on its own, especially since he was a pretty great villain with a lot of his character left more or less ambiguous or untouched by TMA, but it still feels a bit like relying on nostalgia for TMA to flesh out TMAGP's plot and conflict, at least to me. However, all the evidence pointing to it being Jonah could be some kind of red herring to specifically mislead past fans of TMA and set up for a later twist, or we could just be running our minds in circles and drawing conclusions that won't turn out to be relevant to TMAGP so early on. Only time will actually tell, and regardless, I'm really eager to see what happens.

* UPDATE: Augustus is voiced by Tim Fearon, thank you to @lokicat5 for finding that out! We haven't heard him before on this podcast, so he could be either Jonah Magnus's original voice, or a new character entirely.