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)
Factual error: When Fran is on Jeopardy, she gets a Daily Double question and wagers $1,000 dollars. When she answers the Daily Double question though, she buzzes in first and Alex calls on her to answer. Fran would not have needed to buzz in since the Daily Double can only be played by one person.