Continuity mistake: When Jennifer comes into work the next day after her dinner date with Dick, her face is covered in hives from an allergic reaction. Later when Dick interrupts her choral group, the hives on her face have disappeared. She and Dick are wearing the same clothes in both scenes, so she couldn't have overcome such a reaction in such a short amount of time. (00:12:30 - 00:15:00)
Continuity mistake: In 1-2: "Post Nasal Dick", Harry has a dream about Martha Stewart. But in this episode they panic because they dream and have nightmares and don't know what they are. Shouldn't Harry have panicked when he dreamed about Martha Stewart?
Continuity mistake: Dick's plot in this episode is that he learns about the concept of tipping. However, the season 3 episode "Eleven Angry Men and One Dick" showed that Dick was already familiar with the concept of tipping when he tipped a bailiff during a jury selection process.
Continuity mistake: When Ms. Dubcek is showing the Solomons the attic apartment in the pilot episode, they enter (and she later exits) through what is Dick's bedroom in all subsequent episodes. Additionally the staircase at the back of the living room that serves as an entry point is completely missing.
Continuity mistake: When everyone is in the living kitchen, Tommy ends up getting 2 darts stuck into the dartboard. When Harry throws the remote, the 2nd dart is missing. But it's back in the wide shots after Jennifer comes in. Later, when Tommy throws another dart, that 3rd one is seen, but not the 2nd one.