Abstract: You have heard that individual neutrinos are ghostlike and can pass through light-years worth of lead. This is true. So, it may come as a surprise to learn that neutrinos are responsible for much of the heavy lifting in astrophysical environments like the early universe and the gravitational collapse of stars and associated supernova explosions. However, like the hordes of staggering zombies in old horror movies, neutrinos can more than make up for their feeble individual interactions with huge numbers. They can transport entropy, energy, and lepton number through very dense matter that almost no other particles could get through. As a result, they can influence and even dominate macroscopic processes like the creation of the light elements in the Big Bang or the synthesis of the heaviest elements like Uranium in supernova explosions. Plus, neutrinos can act collectively in strange ways which, when coupled with these macroscopic processes, could give us insights into long standing questions about the properties of these mysterious particles.