In the movie-watching spree that constitutes the Ryan & Felicity holiday tradition, I have recently watched partial or complete arcs of the following movie franchises: Back to the Future, Star Wars, Alien, and Terminator. (Small spoilers only — and if you’re not spoiled on this stuff, welcome to my blog!)

Early on in this decadent parade of wonders, Ryan remarked to me that Empire Strikes Back is one of the best movie sequels ever. We talked about that and what it does so well. Then, just now, after rewatching the somewhat lackluster Terminator 3, we watched Terminator Salvation. We had been told it was bad. We decided to try it anyway, out of an unusual completionist urge. (I haven’t watched Alien 3 and don’t plan to, okay?)

Terminator Salvation was great. Surprisingly tightly plotted. New Skynet tech and types were logical, part of a burgeoning machine ecosystem. It was well acted, full of ties to the original movie and winks at the entire Cameron oeuvre.

This has cemented my desire to think (and therefore ramble) about what makes a good sequel (and in part, what does NOT.)

1. A good sequel expands the universe of the original. This should be true of a straight sequel, not just the second act of three. Yes, the viewer loved the first one, but if you rehash the same material, some part of them will wonder why they didn’t just watch it again. Empire Strikes Back took us to new worlds, showed us a hint of the Emperor we’d only heard of, brought us inside the Imperial Fleet.

2. It stays true to the original. This is tricky, but to my English-major self that means it develops at least some of the most important themes of the original. Aliens is a different genre from Alien, and some might argue not a true sequel, but it’s still about the same things: conflict between corporate and human interests, the relationship between human and artificial intelligence, social class, et c. It also means you don’t add a bunch of extraneous new characters that detract from the ones we know and care about.

3. It deepens the characters. The feelings between Han and Leia, the risk-taking prompted by Marty’s insecurity, Ripley’s motherhood…these are things that didn’t exist in the first story, but don’t contradict it. They breathe new meaning retroactively into the first story while using the increased space granted by success (a necessary condition for sequels) to increase the emotional attachment of the audience.

4. It follows through. If we were promised post-apocalyptic guerilla warfare, give it to us. If you hung a craft full of alien eggs on the wall like Chekhov’s gun, take that sucker down and start firing facehuggers. Don’t promise “I’m going to show these people what you don’t want them to see….A world without rules and controls, without borders or boundaries.” and then ignore those people to have boring fisticuffs with infinite agents instead.

5. It rewards the audience’s fidelity. This is perhaps the riskiest part. See number 1 — don’t rehash. The peril of the sequel, especially in action movies, is doing the same thing over, but bigger and fancier. Catch phrases become atrophied, meaningless, a string of checkboxes or gotcha moments. Chases become an obligation, not a thrill. The script serves the formula rather than the story. We didn’t need to see the T-101 shoot up a bunch of cop cars and smugly calculate 0 human casualties in T3. It was something we’d already seen, but shorn of the context that made it relevant in T2. A good reference is something that makes sense in the new context to someone who hasn’t seen the referent. If we haven’t seen Indiana Jones and the Temple of Doom, we don’t scratch our heads in Last Crusade when Indy says “Fly? Yes. Land? No!” Obviously it matters whether he can fly a plane, and his incomplete knowledge creates tension and humor. T4 was full of shots, sets and moments that made devoted fans point and grin, but those things served this movie. Rhyme, don’t repeat.

6. It surprises us. Keeping your promises doesn’t mean being predictable. We have expectations now, and you can play with them. Having the T-101 be the good guy in T2 reversed our expectations. (In T3 it was just a bit tired.) It surprised us. It surprised John Connor. It surprised Sarah Connor into an iconic image of surprise (I know I mentally fall down and backpedal against a waxed floor from time to time.) Set up a love triangle, then knock it down with a relative revelation. Make us expect the repeat, then play against it: a formidable swordsman menaces Indy, he reaches for his gun — but it isn’t there.

Really, what this all boils down to is respecting the original but showing us something new. The Star Wars prequels contradict the originals and depart from their spirit. Star Trek V, among its other sins, takes us past a Galactic Barrier we crossed in the series and acts like that’s where no man has gone before. This is simple stuff, really, but I imagine that deep in Hollywood, making something complicated and expensive with hundreds of other people, it’s easy to forget what you’re really doing. You’re gathering the children by the fire to tell them a story. They say, “Tell us another!” They say, “What happens next?”