Jack Goes to the Dentist - S7-E2
Character mistake: When the dentist is putting cotton in Jack's mouth he neglects to put on rubber gloves first as dentists are supposed to do before any dental work.
Jack Goes to the Dentist - S7-E2
Character mistake: Terri's boyfriend, a dentist, says he took the Hippocratic Oath then corrects himself saying it's only for doctors. Dentists also do take the Hippocratic Oath.
Diamond Jack - S7-E3
Character mistake: At the roller skating rink, Jack looks at the menu on the wall in the snack bar while ordering two sodas and says "What are they... 50 cents a piece?" However, only food items and candy are listed on the menu and drinks are not mentioned at all. How did he know the price?
Character mistake: Maria (Felipe's cousin) supposedly didn't understand any English (only single words like "yes") and would answer (in Spanish) "Que?" after a full sentence of English was spoken to her. However, in front of Jack, one of the girls said to Maria "Tell Jack the new English word you just learned" and Maria understandingly responded "No." There's no way that Maria could respond correctly to that question since she didn't understand any other English sentences throughout the episode.
Character mistake: When Felipe thinks Jack proposed to his cousin Maria, Felipe is happy and congratulates Jack. Later in the episode though, Maria's fiancé shows up and Felipe is shown as already knowing about him. Why wouldn't Felipe tell Jack that Maria was already engaged instead of showing happiness of Jack's "proposal"?
Suggested correction: You missed the entire plot of the episode. Maria's fiancé broke off the engagement, so she went to Felipe's. Then, when he thought Jack had proposed, he was happy. But Jack thought he was happy for offering her a job. Jack then begins talking about Maria as an employee (like trying her out in the kitchen and getting someone to train her). But Felipe thought Jack meant those things about Maria being his wife and got mad at Jack. Then told Jack he's not marrying Maria.
