Voodoo_Chile

So I was watching a documentary and in it there was the tale of Peter Frampton. He had four albums released, each one doing worse than the one before (in his own words) and then all of a sudden he releases a live album entitled 'Frampton Comes Alive' and he breaks records for the biggest selling album of all time (or so I gather). This had me wondering, what are some other albums or singles from relatively unknown artists or bands that sold millions of copies from nowhere? What was their tales? Any input would be much appreciated ^^