Another date between Penny and Stuart (the sales clerk at the comic book store) ends in disaster when Penny calls out Leonard’s name instead of Stuart’s during a make-out. When Leonard finds out, he doesn’t know exactly what to do, but given the thought that he on purpose gave Stuart bad advices on how to proceed on the date with Penny, he gets a bad conscience. Meanwhile, Howard discovers a big design flaw in his NASA Space Toilet, and needs emergency help from his friends, but it may not be enough.