Heather Morris was Beyonce's main backup dancer who was brought in to teach the Single Ladies choreo for an episode. They decided to keep her around as a choreographer and background extra... At least until they realized she could both sing and act too. At that point she slowly turned into a main character. This is what I mean by the magic of the show being, to a degree, an accident. Like half of the original mains were hired to be something else, or were hired last minute and had their characters written around their talents mid-production. That sort of magic cannot be replicated, which is part of why the 2nd gen cast fell so flat. 2nd gen cast was good, but corporate. 1st gen cast was organic.