Character mistake: Watson says that there are fifteen windows on the front of 221B Baker Street, but if you look, there are only twelve.
Character mistake: At the football players funeral, the guy on the left is still breathing, despite being dead.
Character mistake: When the little boy is reading his report about Abraham Lincoln, he states that Lincoln was born in a log cabin in Illinois. Lincoln was actually born in a log cabin in Kentucky.
Character mistake: When Mick arrives at walkabout hotel, Nugget introduces himself to Mick as if they have never met before. Yet in the first movie, Nugget is asking how Mick is getting on in New York. It may be just a case of over familiarity by Nugget but it doesn't make a lot of sense.
Suggested correction: It's quite possible that they haven't met, but Nugget's heard about Mick, e.g. from the people in the bar, stories, etc. Having no doubt heard so much about Mick, Nugget probably feels like he knows him, at least enough to ask how he's getting on.
I think it was just a scene to introduce the audience to Nugget. I'm pretty sure that if Nugget was a regular in that bar, then he must have known Mick.
Character mistake: Buster and June are watching TV, and he says, "Hey, Julie" (the actress' real name). (00:08:07)
Character mistake: When Frank proposes to a hypnotised Jane at the ball game, he says he bought the engagement ring 'this morning.' That morning they were still broken up, with Frank suspecting Jane of setting him up to be shot. They didn't reconcile until immediately before the game.
Character mistake: When Frank opens the present in his office and finds the picture frame from his brother inside, he reads what is supposedly written on the frame out loud: "To Frank, the best brother a guy ever had. Merry Christmas." However, instead of Merry Christmas, it says Love, James.
Character mistake: Cindy tells Greg she hasn't worn curls for 12 years. This is incorrect because in the original series, she changed from curls to braids by 1973 and then to straight hair by 1974. This story takes place in 1988 so technically, she hasn't worn curls in around 15 years (not 12).
Character mistake: Kathy Ireland as Wanda speaks mostly in a slightly squeaky voice. But in one scene she uses her own regular voice.