Factual error: There are many factors concerning Niles' post-operative state which are very inaccurate. After open heart surgery it takes at least three months for the chest bone to heal, Niles would not be able to drive a car for weeks, nor would he be able to lift or twist which he does on the show. Also, he doesn't sport a scar. Your chest bone begins very high up, just below your neck, his scar should have been visible on numerous occasions.
Factual error: Billy, Kim, Rocky, Aisha, and Adam return to Angel Grove in the 1700's...and there are British Redcoats there. On the West coast, in California. England never deployed troops to California, especially considering it was part of the empire of Spain at that time.
Factual error: Early in the show, 3 Marine officers are being questioned about the death of a 4th. All 3 are wearing the Marine insignia on their jacket lapels reversed. [The anchors should point IN, not out] That mistake is corrected for some characters later in the episode, however at least two of the officers are seen later without their jackets, and their shirts do not have military creases - 2 in the front, 3 in the back - standard for a Marine blouse.
Factual error: "Treasure of the Ages": Haskell finds a jeweled cross that's supposedly from a shipwreck hundreds of years old. Only the relic he pulls from the sand is spotless: not a barnacle, rust spot or touch of encrustation on it. After centuries at the bottom of the ocean? Wouldn't happen. (00:02:00)Jean G