Someone already posted the multiverse taxonomy and there are lots of alternative Big Bang models floating around trying to explain weird observations that have accumulated over the years (possible asymmetries of the cosmic microwave background, vast cosmological voids, old objects in the early universe, "Dark Flow", etc), and some of them postulate that what we call "the universe" is a sort of sprout from an older, larger universe. Conversely, our own universe may be sprouting. In those models the weird observations are explained either by the "history" of the universe as a sprout or by new sprouts in our own universe.