At 43:53 and 44:17, the same three extras walk past in the background, in the same direction.
Wednesday says that she can determine that Gomez is lying because she recognizes his "tells" from when they played Russian roulette. Tells are an indicator that someone is being purposefully deceitful, such as in a game of poker when one wishes to hide the strength or weakness of their cards. As the results of Russian roulette are completely up to random chance, there is no opportunity to try to lie to your opponent.
The young Gomez is much taller than Morticia. The old Gomez is much shorter than her. The supernatural attributes of the Addamses allow for some leeway here.
The Ford Explorer model shown in 1990 was first produced in November 1994.
When the session with Dr Kinbott is over, the cuckoo clock goes cuckoo twice, even though the clock hands show it is one o'clock.
When Wednesday talks with Principal Weems about Judy Garland, the yearbook page she holds up has a photo labeled "Morticia Trump" rather than Frump.
The show quotes "Fire will rain" in Crackstone's crypt as well as a message burned into the lawn. Then when the characters are inside the Gates mansion the altar reads "Blood will rain." Whether the error is on the altar or in the message burned on the yard, the mastermind would have not made that mistake.