Mrs. Huxtable Goes to Kindergarten - S5-E14
Continuity mistake: In the previous episode they got a new couch, in this episode the old one is back.
Cyranoise de Bergington - S5-E8
Other mistake: During the opening scene, Cliff is in his home office, located in the basement of his home. The phone rings. He walks over to his office desk, then presses the speaker button. An unfamiliar female voice is heard speaking, as she states that someone is there is see Cliff. Who is that woman? Where is her office desk stationed? She is never heard, or seen, ever again within this episode, and throughout other episodes, prior or after. This is S5E7. This website has the season and episodes mismatched. (01:19:00 - 01:39:00)
Suggested correction: It sounded like Clair to me. And in regards to who that someone was, it was Rudy. So it wasn't as if it was Dr. Huxtable's secretary announcing a patient, or a secretary who didn't know who Cliff's kids were. It's easy to picture Clair acting like a secretary for her daughter's sake so that Rudy could come in and talk to her dad while he's a work, without Rudy just running in and disrupting him. Plus, his phone didn't ring, it was the intercom that Clair would have used from another phone in the house.
Clair is not seen speaking into a speaker, at any time, during any episode, throughout the entire show's existence, and that woman's voice does not sound like Clair's. In addition, Cliff exchanged with 'the mystery female' in a professional manner/tone of voice, like a boss would to an employee, an not in his usually playful, loving voice, that he normally speaks to Clair with.
Audio problem: After Jade enters the coffee shop she says "Dennis, Darling!" and immediately afterwards you can hear a crew member/the director saying "Cut." Then the scene continues from a different camera/angle. (00:07:20)
Continuity mistake: When Vanessa and Rudy are at the table, the amount of orange juice in Rudy's cup changes a couple of times.
Plot hole: At the beginning of the episode, Theo, Vanessa and Rudy all act as if they forgot Clair's birthday. But Rudy already had a present for her mother's birthday, the pendant she ordered in the episode, "Cyranoise de Bergington".