While it's unlikely there's any real danger of a 'Moonlighting' situation with Sheldon and Amy on 'The Big Bang Theory' (Thu., 8PM ET on CBS), they nevertheless moved their relationship the tiniest increment forward. It has been a year after all, so why not.
Because they weren't really anything official, Amy was receptive to Stuart asking her out on a date. Sheldon found himself consumed with anxiety and jealousy and finally decided that he had to act fast. So he crashed their date.