Sleeping with the Enemy - S3-E6
Character mistake: Noel Shempsky (the supposed Star Trek Nerd) attributes the quote "The needs of the many outweigh the needs of the few or the one" to James T. Kirk, when it was Spock who said it. (00:03:50)
A Long Walk To Pittsburgh (2) - S4-E17
Character mistake: In this episode Cory says that Topanga gave him his first kiss at age 13, but their first kiss actually happened when they were 11, in the 6th grade. (Season 1 - Episode 7 Cory's Alternative Friends).
One False Mole and You're Dead - S5-E12
Character mistake: CC, when talking about the Marie Antoinette show, says that Louis and Marie had two children. They actually had four children (Marie Therese, Sophie, Louis Joseph, and Louis XVII).
Character mistake: When Clark flies to see his parents for the first time, he is wearing a maroon shirt and jacket. When he lands at his parents farm he is still wearing his jacket and maroon shirt. In the next shot, he has taken his jacket off which now has a rip in the shoulder, as he enters the house his shirt is blue, and then in the following shot at the table having dinner his shirt is again maroon. (00:30:00 - 00:30:50)
Cat on a Hot Steel Beam - S1-E60
Character mistake: As the fire truck darts out from a back alley, the sign on a nearby gift shop window reads "gift's" when it should be "gifts".