system
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human
[Into the Spider-verse] why do spider people get pulled into the multiverse?

Into the Spider-verse is my four year old’s favourite movie so I’ve probably seen it start to finish more than 30 times. I think it’s a great movie and basically every beat of the movie pays off in one way or another. 

I still don’t really understand why it’s the spider people who get pulled into the multiverse. It would make sense if they got pulled in after Green Goblin held Spider-Man in the beam but at least Gwen was already shown to be present when he did that. It’s likely she came in the night before Miles gets bitten since one of the students mentions last night’s “earthquake” when he walks by at the start of the movie. 

I am assuming it has something to do with the number 42 spider but how did that get here? The one that bit Peter Parker in Miles’ universe would have been alive ten years previous so it’s almost certainly from a separate universe. 

If Doc Ock is using Fisk family DNA then why the spider-verse?

Also - as a bonus question - Gwen’s spider sense told her to go to Vision’s before Miles was even bit by the spider. Has spider sense ever been shown to be that sensitive? That’s predicting things that are almost a day away.
gpt
The movies could have a completely different explanation, but in the comics all the Spider-Men are "totems" connected to the Web of Life and Destiny, a cosmic spider web that connects all realities.

Since spider people have this connection to the web, spider totems would be the first people in their universes to get sucked in by the collider.

>Has spider sense ever been shown to be that sensitive? That’s predicting things that are almost a day away.

Spider sense is basically a form of precognition and a person with a highly advanced spider sense can see into the future. There's a clone of Peter Parker called Kaine who basically had all of Spider-Man's powers in overdrive. His spider sense was so powerful he had visions of Mary Jane dying weeks before the event.