Recently, John Semper Jr., writer and producer of the Spider-Man animated series from the 1990s, debunked a rumor that the 1990s Spider-Man would appear in Into the Spider-Verse 2, but at the same time, Semper also discussed his feelings over what he feels are a lack of credit over creating the very concept of the Spider-Verse.
The final episodes of the 1990s Spider-Man series were a two-part episode called "Spider-Wars," where Spider-Man travels to an alternate reality where that dimension's Spider-Man had merged with the Carnage symbiote to become Spider-Carnage. That universe's Spider-Man teamed up with Kingpin, Alistair Smythe, the Hobgoblin and the Green Goblin to raze that dimension's New York City. Spider-Man teams up with a group of Spider-Men from other dimensions to defeat Spider-Carnage. Naturally, Semper feels that that storyline was the inspiration for the Spider-Verse.
The direct inspiration for the film, Into the Spider-Verse, was the 2014 Spider-Man event, "Spider-Verse," by Dan Slott. Slott explained that his inspiration was the Spider-Man video game, Shattered Dimensions, which he wrote the story for and thus decided to take that concept and make it appear in the comic book universe, as well.
When someone asked Slott about whether "Spider-Wars" was an influence, he replied, "Not really. It was off my radar till people brought it up after Spider-Verse was over. I saw Spider-Man Unlimited as a continuation of that series, so I felt we had it covered. We had tentative plans to involve them if there were a sequel (Spider-Geddon), but it fell to the side.
Semper, though, naturally disagrees. He explained on Facebook, after debunking the Spider-Verse 2 rumors:
I do mention that I created the Spider-Verse whenever the subject comes up, mostly because I enjoy needling Sony/Marvel, and I hope word will get back to them that I’m mildly pissed at not even being thanked at the end of their first film. But I don’t lose much sleep over it, and no – I don’t need “therapy,” as someone rather rudely suggested. In fact, I only talk about the Spider-Verse when somebody else brings it up. When this bogus rumor circulated yesterday, a lot of you approached me with the news here on Facebook, so it was hard for me to avoid talking about it.
Finally, a few of you seem to be irritated that I even assert that I created the Spider-Verse. Yeah…tough. I can’t help you there. I know what I originated, and how much of it I saw in that movie and my stance is unchanged. The whole narrative underpinning of that film – that a group of Spider-Men from different realities had to band together to prevent a rift in dimensions created by the Kingpin from destroying all of reality - yeah, I thought that up. If you can’t accept that, I can’t waste time arguing with you. The proof is in my series itself.
Source: Making of Spider-Man the Animated Series on Facebook