Flow of time

[Astronema]

They introduced a new concept this expansion: interdimensional fusion. If the fusion takes time to complete, then time could be unsynced while it's happening and synced once it's done. That could be one explanation. But the idea of interdimensional fusion as a process is kind of hard to comprehend. Like a dome appeared and some people from our world got trapped in it while the fusion was incomplete?...

They stole this trope from the failed last season of the TV series sliders. A dr. Geiger uses a fusion device called the combine to experiment in fusioning dimensions.

[Cleretic]

They stole this trope from the failed last season of the TV series sliders. A dr. Geiger uses a fusion device called the combine to experiment in fusioning dimensions.

Far more likely is that it's riffing on Final Fantasy IX, which was approximately concurrent with Sliders' last season. The plan laid out in IX never really got put into play, but the description more or less lines up. Hardly 'stolen'.

And of course even then it was a reiteration on Final Fantasy V's story, and over the years similar ideas have cropped up in Doctor Who, Xenoblade, both DC and Marvel comics (including DC and Marvel together in 1996) and more examples that I haven't really got the time or interest in cataloguing. I wouldn't call this a common trope, it's not especially often that a story winds up in a situation to do it, but it's fairly plentiful to the point where Final Fantasy's done it a few times.