Complex sentence: , the episode takes place in the alternate universe's version of Manhattan, whose name is spelled with only one T. One notable difference in the alternate universe is that while the September 11 attacks occurred, the World Trade Center towers were not destroyed.
Split into simpler sentences: , the episode takes place in the parallel universe's version of Manhattan, which is spelled with only one "t". One key change in the parallel universe was that while the September 11 attacks occurred, the World Trade Center towers were not destroyed.