Have I ever seen this plot development, or am I crazy?

Very true, allthough I believe the ‘slayer axe’ might have had something to do with that. It must be said they also turn this one around once in a while. Somewhere in season 5 Buffy is taken down and stabbed in the abdomen by a regular vampire (the type she has killed hundreds of). They even have the other characters be surprised there was nothing ‘special’ about the vampire.

The corrosive blood was accounted for, but after the first film it was greatly reduced in potency. The wikipedia entry says: Ron Cobb suggested the idea that the creature have acid blood as a plausible means to make the creature “unkillable”; if one were to use traditional firearms or explosives to attack it, its blood would eat through the hull of the ship.

If the potency had stayed the same beyond the original film, every dead or wounded Alien would sizzle his way hundreds of feet downward.

This is played out hilariously in a Robot Chicken skit.

I’m reminded of the original Doom. At the end of episode One, the big bad supermonster you fight is… a Baron of Hell (two of them actually). By the time Doom II rolled around a Baron was welterweight at most.

I believe Lupin was only teaching Harry the Patronus Charm. I haven’t read the book in a while, so I might be overly relying on the movie.

You are correct. Lupin explicitly tells Harry that the Patronus charm is well beyond Ordinary Wizarding Levels, thus there is no reason he would be teaching it to third years.

I believe that the Patronus charm is normally taught in Year 5. Harry learned it in Year 3 since he was having trouble with the Dementors at the school. He taught everyone in Dumbledore’s Army it during Year 5 when Umbridge was in charge and they weren’t allowed to learn anything…

I think you’re right - I was confusing patronus with riddikulus.

This happens in the Matrix sequels. The agents are explained in the first movie as being so powerful, that no one has gone up against one before and survived. But in the sequels, Morpheus and Trinity fight both early versions of Agents (which were supposed to be just as powerful, but harder to control) and new upgraded Agents. And they do a pretty decent job.

This was what I thought immediately upon reading the OP.

While the potency of the acid may well have varied (though the first direct sign the marines find in Aliens is a big hole eaten through multiple floors of a colony building), I think the biggest change is that in Aliens, they were mostly in buildings with a solid foundation and with a breathable atmosphere outside. That makes the acid much less of a threat. Sure, it may eat all the way down to bedrock, but it won’t take all the breathable air with it.

We also don’t get a whole lot of information on the capabilities of the acid. We know that it’s scary stuff and eats through metal in seconds, but not much about what it does to other materials. I don’t recall if it made it into the film or not, but it was mentioned in some revision of the Alien script that the acid was stopped by a layer of asbestos, so it was at least considered that it was less effective against some mineral materials. We might conclude from Aliens that it is also less active against organic materials than against metal (otherwise, Hicks would have had holes burned all the way through his dead by the spray).

I dislike all the later movies and haven’t watched them enough to remember what they offer in relation to the acid. Whatever it is, it probably sucks and is wrong.

As brilliant as Zelazny could be, and as much as I loved the first few volumes, his Amber stories tie with King’s Gunslinger series for getting weaker as they go along.

Every fifth page of the Lensman series introduced a new, mind-bogglingly ether-searingly incandescent beam that makes the one he introduced five pages ago seem like a rather feeble flashlight by comparison. The English language simply did not contain enough superlatives to keep ol’ Doc Smith in business.

Ehhh. I’m not clear what you mean.

They didn’t fight the ubervamp army until the finale. The first Uber-vamp was dispatched about mid way in the season by Buffy. After seriously kicking her ass for a while.

I think the point brought up earlier was that the Ubervamp army should have decimated the Slayers-In-Waiting nearly instantly. Even after they all “got the power.” Buffy an experienced slayer had trouble with one of them. Ill-trained girls even with Slayer powers should have been no match.

However I don’t think we see anyone but Slayers killing them. Andrew and Anya only fought Bringers.

I think it was in *Innocents Abroad *that Mark Twain tells how an unscalable mountain is finally conquered after dozens have tried and failed to do so, some dying in the attempt, and a decade later grandmothers are casually strolling up the peak carrying picnic baskets. He may have been exaggerating.

In the early seasons of Farscape a big deal was made about how tough Scarrans were, the few we see far away from their territory in the second season take dozens of shots to take down and stop them moving.

By the fourth season when the characters are in Scarran territory and they are one of the big bads they are taken down by the car load no problem.

And the Goa’uld. Took years to kill 'em off, and even then one managed to time travel to mess things up for humanity.

I try to rationalize that as the Scarrans sending the badasses to handle solo missions away from support–of course they’re going to be tougher than the ones who stay at home. The analogy that comes to mind is that the ones they fight early on are Navy SEALs; most of the ones they fight later are mall rent-a-cops.

There might also be an element of “You know that spot where you shot him last before he went down? Try shooting that spot first next time.” That’s actually something that applies to this pattern in storytelling pretty often. The first time you do something is generally the hardest. You learn things in the process, so next time, maybe you know better what supplies to pack, or where the weak spots are, or whatever. Of course, that doesn’t account for a grueling months-long trek in harsh conditions suddenly becoming a day trip, but it does excuse some cases of diminished difficulty.

Time travel in Star Trek. By the time of the one where they save the whales, it is practically routine.

And by sometime in the 29th Century had become so routine they had time cops. Of course, I’ve always assumed they used the Guardian (or at least Guardian-based technology) for that.