One instance was a simple chat about shopping, which led to an idea that all shopping malls should have women only massage parlour where weary females could go for an erotic massage, and that led to ideas for a full "health spa" on the same level, with orgasms a major part of the treatment as they burn so many calories, and....well, let's say the ideas being exchanged got pretty hot leading to....it was fun, though. I actually used the idea in one of my stories, Love Thy Neighbour 2: Shopping With Alison.