Freaky citizens - CGI. Or use old footage from A Boy And His Dog.
Fire dress - Use a papier-mache sculpture of Jennifer Lawrence. Have her jump out of the way and really, really quickly shove the sculpture into the frame. The sculpture should be on wheels so this will look as seamless as possible. Make sure that the sculpture is already on fire or it'll look pretty awkward.
Muttations - Train dogs/wolves/lizards to run around and kill people. Find freaky-looking ones to really sell the effect. But make sure that they only end up killing extras, for obvious reasons.
The final battle - Really amazing CGI. Like, Sliders amazing.
Buttercup - Get a cat. Shave it. Or get a small dog and pretend it's a cat. Glue weird things to it, like a lobster tail. Just ugly-bling the hell out of that animal.
Imaginary Lands - For the pink sky, use a big piece of pink crepe paper. Make sure it's really big, though, or the camera might catch the edges. But don't worry: it doesn't have to cover the whole sky or anything.
Awful Katniss - Dramatize Katniss' internal conflict with a little imp that sits on her shoulder and tells her what to do.
The Toddler Massacre - I've got nothing here. Just kill a bunch of children, I guess.
Nudity - Warwick Davis as a body double.
Perhaps part of what we're talking about here (to some extent) is a distinction between the empirically real and the virtual. DS9 has a particular vision of the virtual that involves a tremendous amount of resources to create a compelling reality for one or two parties. The actual virtual - the one that we've developed over the last decade or so - is made up of networked interactions with real people. We've made a primitive Holodeck out of social media, one that is more powerful and enchanting by virtue of its mass participation and input of multiple real agents into a virtual social space. Star Trek's creators predicated their show on a fantasy of centralized machines with vast resources to make those machines run. We've broken those imagined machines into little pieces, and the control that affords us has given us ample opportunity to waste our time.
I would have put this down to a historical blindspot, but I think that Ronald Moore is really freaked about the notion of a networked communal mind. In BSG, he went to great lengths to explain why the Galactica wasn't networked in any way - and then he pitted it against a race of machines that pretty much did nothing but slaughter humanity and screw around in virtual environments. The cylons get plenty of sympathy as the series goes on, but it's interesting that the enemy of humanity bears more resemblance to us in some ways than the heroes of the show.
EDITED TO ADD: Blah blah blah.
That's a great line? In that case I've got a few more.
"What is it about this Denny's that makes everybody into a crazed killer?"
"What is it about that gazebo that makes everybody into an accredited life coach?"
"What is it about this taco meat that makes everybody into a zombie?"
RIVER SONG: So what do you do?
[pause]
DOCTOR: I travel. Through time.
[pause]
RIVER SONG: Is it dangerous?
DOCTOR: [smiles]
[pause]
[pause]
[they kiss]
[Amy gets shot]
[The Doctor kicks The Master to death]
THE END
[pause]
"One last time? What do you mean?"
"Oh... yeah... well, see you 'round."