This is sort of a catch-all for two categories that didn't quite deserve their own pages: monologues that start out as a voiceover, and then turn into someone talking to the camera; and voiceovers that are just sort of demented, silly or satirical. They're both a bit different from your standard science fiction voiceover, in any case.
Here's the classic example of a voiceover that turns into a conversation. Joss Whedon's big movie debut starts out with a whole cosmic theme, as a woman talks to us about how we (once again) messed up the Earth and had to colonize a new solar system. And then suddenly, we're in the room with the woman, and it starts a whole new scene. Which turns into something else, which turns into something else.
Here's another voiceover that turns into someone talking to us. Guillermo dell Toro's early classic starts off with a male narrator telling us about the awful plague that struck... and then we're in a hospital with him, uncomfortably close to those plague victims. Aaaaa!
Megiddo: The Omega Code 2:
I love this Godsploitation movie's beginning so much. It starts out as an echoey ominous voiceover, with some guy reading Scripture, and then it turns into a sweeping apocalyptic montage, with that voice droning over it... and then suddenly, we're hanging out with that guy, and he's just having a regular conversation. He just happened to be quoting scripture and droning ominously in the course of his chat. To be fair, this is Satan.
And then, we effortlessly segue into our comedy voiceovers portion. This Garry Shandling movie feels the need to start off with a deep booming voice, letting us know Garry Shandling has no penis. It's important information that we'll need for the rest of the movie, so it's good to get it out there right away.
And then finally, there's this cheesy British space comedy, which tries to play up our expectations that visitors from outer space will be brilliant and noble, so the movie can shatter them. (Of course, we already know we're watching a movie called Morons From Outer Space, so good luck with that.)
Somehow, I remembered this opening monologue being longer and more crazy, but I guess they're saving that for later in the movie. As it is, you could almost be fooled into thinking you're watching a serious space epic.
I almost didn't include this one, since it's so short and kind of meh. (I already had 50 voiceovers, without this one.) I think the "imagine the furthest point in the universe. Our story begins just a couple blocks past that." I think they're trying for a Douglas Adams "space is big" vibe... and then they just give up and go home.