Ultimate crossover / world jumping interest check!
The idea here is, in essence, to take a character that we like from a series, make them come from an alternate version of that world (steampunk Star Wars, film noir Scooby Doo, etc) and throw them all together.
As far as why this is happening, the concept is thus: there are an infinite number of parallel realities, each different from the others. This means that there are plenty of realities that have developed the technology or magic to move between realities. This has led to several inter-world groups, the important one for us being the Infinite Patrol- basically think interdimensional police. The players are a squadron on this group, with one catch- they are the worst. Either unreliable, reliably violent, or something else, there's a reason they're still doing the 'grunt work' and chasing hoodlums across realities.
As far as what kind of characters you can play, there's not many limitations- they do have to be a canon character from somewhere, no OCs, but you are welcome and encouraged to drastically change what kind of world they came from. You can go into as much or as little detail as you like on their origin world, as long as you manage to illustrate how it shaped them to be as different as they are from the original version of that character. Live action shows, cartoons, games, books, all are fine. If you pick a super powerful character though, I won't stop you but please tone the power down a bit so that you don't just radically outstrip everyone else.
As an example character, I'm intending to play Rarity from MLP:FiM. Thing is, the Equestria that she's from is a lot closer to Shadowrun, with technology being on par with magic instead of lagging far behind. This has led to the Diamond Dogs, who lack magic, to be far more dangerous (their hands are much better adapted to using tools such as magic-enhanced assault rifles, after all) and allowing them to establish a stranglehold on a large portion of the criminal underworld. Rarity wound up working for them, starting out as a tailor for a gang before her eye for gemwork was noticed. She eventually wound up doing weapons work, her ability to create perfect lenses for scopes and her attention to detail meaning that she was very, very good at weaponcraft.
As she later discovered, her reality only got the way it did because it had been 'contaminated'- there had been influence from another reality before they were capable of reaching out and exploring by themselves. Normally, worlds that aren't capable of travel between realities are left alone, protected by Infinity Patrol law, but once it was realized that it was a contaminated world, offworlders started arriving.
It turned out that Rarity was actually quite dangerous with needles and thread, and her long time working for criminals had left her with a sociopathic streak. Seeing her potential use, she was recruited by the Infinity Patrol (as much to have her help as to stop other organizations from getting her) and she's worked there since. She does her job well and she likely would have been promoted further up the ladder, except for the fact that she is WAY too quick to resort to deadly force, often mucking up the original goal of the mission.
I hope I got across what I'm going for here. I'm happy to answer any questions!