A slight--humming is the wrong word, but everything else is more wrong--fills the bar. For a moment, it seems completely ridiculous to mistake Heylel for a human, although what she would be instead is...non-obvious.
And then it is over, and she is merely a tall woman.
"Well," she says. "I know what's going wrong with your kids, anyway. Not that I'm sure how to explain it to someone who probably doesn't have a grasp on Mendelian inheritance. Um...angels have a thing in their bloodlines, and mortals don't, and if you're an angel you can pass on the thing to your kids or not, and a Lucifer has the thing from both parents, and that's too much."