How about Lum Invader and Kazami Mizuho? Speaking of Onegai Sensei, there is also her descendant Takatsuki Ichika, so maybe they can pair up together. You can technically label To Love Ru's Lala as an alien as well and have her pair up with Lum. If anything, there's also FLCL's Haruko and Asobi ni Iku yo's Eris, if you want to try them out.
I was thinking any general theme that would use 4 characters from 4 different anime, but vampire seems to be a good one, thanks. At least, I can't think of 4 aliens popular enough to be exhibited, or something.
Hi. Do you have any other themes that are similar to time traveling? Please post the response on my profile so it notifies me.
Themes similar to time traveling? Are we talking about science fiction or non-humans as a whole? I am sure there are a bunch of things that can be used as themes. Maybe a vampire match with girls like Makashiya Moka, Maaka Karin, Arcueid, and Miyu. Maybe celestial beings like Belldandy, Kannabi no Mikoto, Nagi (Kannagi), and Lisianthus (Sia), if that is what you are talking about. If not, I'll try again.