Pretty much all of my characters are made as half a duo with my fiance. (Duo pro tip - both take Grant Invisibility, which is better than both taking stealth and don't require two moves like Invisibility)
Usually we paired up based on origin and complementary ATs, as opposed to just theme, but the themes wouldn't be so far off - like a pair of psionic aliens (one brute, one controller).
The two most recent pairs we did were a member of the Red Torch Corps and the Blue Torch Corps, and making our favorite Pokemon as heroes to team up. (Well, actually, as villains, since they are Crobat and Glalie, not the most heroic of Pokemon.) We joked about getting other people in on that and making a Pokemon SG.