Once again the doctor has been tinkering with his programming, this time to add daydreaming to his subroutines (this has some parallels to Data's development in TNG). Unfortunately, he constantly loses himself in these dreams, even in the middle of senior staff meetings. And he not only dreams of saving the crew as the captain of Voyager, but also has an all too vivid imagination when it comes to the ladies on the crew...
After an alien species (which for a change has been designed to look really strange and not just have slightly different nose ridges) taps into the doctor's mind to secretly find out more about Voyager and its crew, they are confronted with all of his daydreams which they consider to be reality. Since the doctor also destroys Borg in his dreams and developed a superweapon, the aliens are planning a full-scale attack on Voyager because they see it as a threat. However, the crew has an ally on their side with one of the aliens on board the alien ships. The doctor has to impersonate the captain (with a lot of overacting) in order to use this charade to convince the aliens that they shouldn't mess with Voyager!
In any case, the scene before the opening credits is hilarious and reminds me of the SNW episode "Subspace Rhapsody", in which the actors interpreted the story by singing and dancing. Robert Picardo is once again at his peak in this episode.
By the way: In one of the dream scenes, Seven poses naked for the doctor, who is drawing her. But to the chagrin of all pubescent boys, her two special talents are not visible.