Okay, so I was just over at the Gaming As Women blog (http://gamingaswomen.com) and saw an ad for a Kickstarter project about a game where you play a mastermind and a minion seeking to take over the world. In a typical RPG then, you'd be playing two characters. Personally, I don't like playing more than one entity at a time in RPGs. I avoid classes which have an animal companion, etc. It's not that I don't like companions/hirelings/apprentices/etc., it's that I find it too distracting. The Kickstarter ad reminded me that a while back I came across a blog post somewhere (don't remember where, sorry) about a dragonrider campaign. In the campaign each player would roll up a rider (their main PC) but also play the dragon of one of the other players. Thus each dragon would have it's own distinct personality and you'd have great interlocking roleplay going on between the riders, dragons, and players. I love that concept!
Then I thought, hey, you could easily extend that concept to lots of other types of game:
Wizards + apprentices
Knights + squires
Masterminds + minions
Superheros + sidekicks
Druids + animal companions
Mecha Pilots + intelligent mechs (a sci-fi take on the dragonrider concept)