Dennis' remark, "We don't give a shit about your dream," is a direct call back to the first episode of the first season, "The Gang Gets Racist," in which Dennis stops Dee from telling him her dream by interrupting, "I hate listening to people's dreams. It's like flipping through a stack of photographs. If I'm not in any of them and nobody's having sex, I just... don't care."
The trivia item below may give away important plot points.
Scott Bakula played Samuel Beckett in the popular 1980s series, Quantum Leap, where every episode would end with him leaping into a different person in a different time. That person would then look in the mirror and Sam would see his reflection and disclaim, "Oh boy," in the same way he did at the end of this episode.