Uh... Let's see what I can say without saying anything about how the story plays out...

Let's put it in a hider, actually. It's a very vague plot overview that gives a basis of what I'm using my ideas for.
[hider=Pseudo-spoiler except Not Quite?]
So in Steins;Gate the main cast (Okabe, Daru, Mayuri, Kurisu) find out that the Future Gadget No.8 that Okabe and Daru have created is able to send text messages back into the past. Stuff happens, Okabe finds out that when the timeline shifts, he retains memories of events from other timelines, etc;. Then it gets upgraded into a machine that can send memories into the past. Stuff happens.

This is a very vague overview of Steins;Gate that honestly does it no justice. Watch it on your own time, but for now this small overview will do.

Anyhow, what I had in mind was that these characters who have traveled over multiple universes already have what Okabe dubs his 'Reading Steiner' aka ability to keep memories over timelines, so they end up in the Steins;Gate world in order to secure/destroy/whatever the Phone Microwave for their own purposes.

I ain't spoiling the rest of the story, alright? :I
[/hider]