Suppose a person was wandering around the video store and picked up two (or more) movies, with the mistaken thought from the titles that they were sequels, which mistakes do you think they’d be in for the biggest shock if they watched them back to back without bothering to read the movie’s description?
I think any poor soul who picked up 28 Days and 28 Days Later might have a moderate startle. 
Oh, and for the holiday season Rudolph and Reindeer Games.
Others?
Oh, I dunno… I kinda like the idea of rage-driven zombies massacring Sandra Bullock and those whiny, self-pitying drunks and druggies.
If you thought Free Willy was a sequel to The Net you’d be in for a movie-viewing shock.
If you thought Malice was a sequel to Absence of Malice you’d be in for a movie-viewing shock.
You mean, like, if you liked SINGIN’ IN THE RAIN so you took out THE RAIN MAN ?
If you thought Highlander II was a sequel to Highlander, well…
Oh, touche.
Costner’s The Postman is not a sequel to The Postman Always Rings Twice, unless a lot has changed in the meantime.
I can find Henry, Henry IV (in two parts), and Henry VIII, but none of the others in the series.
Dunno about Henry, there is a Henry VI (it’s a 3-parter!), but you missed the best: Henry V.
Ticks me off that they skipped Richard I and went right to Richard II and Richard III
If you thought STEEL DAWN was a sequel to RED DAWN…
If you thought DAWN OF THE DEAD(2004) was a sequel to NIGHT OF THE LIVING DEAD (1990)…
I’m convinced The Ring was only popular because people thought it was a sequel to The Lord of the Rings.
And wasn’t Rocky a sequel to The Rocky Horror Picture Show? Heck, there’s five of them.
I often searched for the precursors to Bill Coby’s Ostrich riding superhero movie, Leonard Part 6.
Also; I was confused when “Before Sunset” and then “After the Sunset” were released within months of each other this year.
If you thought <b>Blue Velvet</b> was a sequel to <b>National Velvet</b>…
The Rocky Horror Picture Show was actually a sequel to The Last Picture Show.
If you thought Red Dragon was the sequel to Reign of Fire… well, you might be pleasantly surprised.
Valley of the Dolls and Beyond the Valley of the Dolls
They’re over on the shelf by Malcolm IX and Malcolm VIII.
Obviously, K-19 is a sequel to K-9.
And Cabin Fever is a sequel to Cabin Boy.
1984 was the long-awaited follow up to 1941.
It’s little known that Naked Lunch is in fact a sequel to Breakfast at Tiffany’s.
Well, I mean it could be…from a certain point of view.
Would My Dinner with Andre or Eating Raoul be the sequel to those?